ssl-opt.sh: Simplify the implementation of the -l option

Instead of verifying if the LIST_TESTS variable has been set in
every function to avoid using the P_QUERY variable and avoid
calling a program that has not necessarily been compiled yet:

 * Define P_QUERY=":" when LIST_TESTS has been set.

Signed-off-by: Tomás González <tomasagustin.gonzalezorlando@arm.com>
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 31114c9..b925a01 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -210,6 +210,7 @@
 if [ "$LIST_TESTS" -eq 0 ];then
     CONFIGS_ENABLED=" $(echo `$P_QUERY -l` )"
 else
+    P_QUERY=":"
     CONFIGS_ENABLED=""
 fi
 # Skip next test; use this macro to skip tests which are legitimate
@@ -223,9 +224,6 @@
 # Check if the required configuration ($1) is enabled
 is_config_enabled()
 {
-    if [ "$LIST_TESTS" -gt 0 ];then
-        return 0;
-    fi
     case $CONFIGS_ENABLED in
         *" $1"[\ =]*) return 0;;
         *) return 1;;
@@ -234,9 +232,6 @@
 
 # skip next test if the flag is not enabled in mbedtls_config.h
 requires_config_enabled() {
-    if [ "$LIST_TESTS" -gt 0 ];then
-        return;
-    fi
     case $CONFIGS_ENABLED in
         *" $1"[\ =]*) :;;
         *) SKIP_NEXT="YES";;
@@ -245,18 +240,12 @@
 
 # skip next test if the flag is enabled in mbedtls_config.h
 requires_config_disabled() {
-    if [ "$LIST_TESTS" -gt 0 ];then
-        return;
-    fi
     case $CONFIGS_ENABLED in
         *" $1"[\ =]*) SKIP_NEXT="YES";;
     esac
 }
 
 requires_all_configs_enabled() {
-    if [ "$LIST_TESTS" -gt 0 ];then
-        return;
-    fi
     if ! $P_QUERY -all $*
     then
         SKIP_NEXT="YES"
@@ -264,9 +253,6 @@
 }
 
 requires_all_configs_disabled() {
-    if [ "$LIST_TESTS" -gt 0 ];then
-        return;
-    fi
     if $P_QUERY -any $*
     then
         SKIP_NEXT="YES"
@@ -274,9 +260,6 @@
 }
 
 requires_any_configs_enabled() {
-    if [ "$LIST_TESTS" -gt 0 ];then
-        return;
-    fi
     if ! $P_QUERY -any $*
     then
         SKIP_NEXT="YES"
@@ -284,9 +267,6 @@
 }
 
 requires_any_configs_disabled() {
-    if [ "$LIST_TESTS" -gt 0 ];then
-        return;
-    fi
     if $P_QUERY -all $*
     then
         SKIP_NEXT="YES"
@@ -311,9 +291,6 @@
                                        MBEDTLS_KEY_EXCHANGE_RSA_PSK_ENABLED"
 
 requires_key_exchange_with_cert_in_tls12_or_tls13_enabled() {
-    if [ "$LIST_TESTS" -gt 0 ];then
-        return;
-    fi
     if $P_QUERY -all MBEDTLS_SSL_PROTO_TLS1_2
     then
         requires_any_configs_enabled $TLS1_2_KEY_EXCHANGES_WITH_CERT
@@ -340,9 +317,6 @@
 }
 
 requires_config_value_at_least() {
-    if [ "$LIST_TESTS" -gt 0 ];then
-        return;
-    fi
     VAL="$( get_config_value_or_default "$1" )"
     if [ -z "$VAL" ]; then
         # Should never happen
@@ -354,9 +328,6 @@
 }
 
 requires_config_value_at_most() {
-    if [ "$LIST_TESTS" -gt 0 ];then
-        return;
-    fi
     VAL=$( get_config_value_or_default "$1" )
     if [ -z "$VAL" ]; then
         # Should never happen
@@ -368,9 +339,6 @@
 }
 
 requires_config_value_equals() {
-    if [ "$LIST_TESTS" -gt 0 ];then
-        return;
-    fi
     VAL=$( get_config_value_or_default "$1" )
     if [ -z "$VAL" ]; then
         # Should never happen
@@ -386,9 +354,6 @@
 # Inputs:
 # * $1: protocol version in mbedtls syntax (argument to force_version=)
 requires_protocol_version() {
-    if [ "$LIST_TESTS" -gt 0 ];then
-        return;
-    fi
     # Support for DTLS is detected separately in detect_dtls().
     case "$1" in
         tls12|dtls12) requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_2;;