Fix guard in ECJPAKE tests in ssl-opt.sh

Three tests were guarded by `MBEDTLS_KEY_EXCHANGE_ECJPAKE`,
not `MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED`, as it should be.

Curiously, the guard still functioned as intended, perhaps
because `MBEDTLS_KEY_EXCHANGE_ECJPAKE` is a prefix of
`MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED`.

Signed-off-by: Hanno Becker <hanno.becker@arm.com>
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index e7849cd..1ebab3e 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -5740,7 +5740,7 @@
 
 # Tests for EC J-PAKE
 
-requires_config_enabled MBEDTLS_KEY_EXCHANGE_ECJPAKE
+requires_config_enabled MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED
 run_test    "ECJPAKE: client not configured" \
             "$P_SRV debug_level=3" \
             "$P_CLI debug_level=3" \
@@ -5754,7 +5754,7 @@
             -C "found ecjpake_kkpp extension" \
             -S "None of the common ciphersuites is usable"
 
-requires_config_enabled MBEDTLS_KEY_EXCHANGE_ECJPAKE
+requires_config_enabled MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED
 run_test    "ECJPAKE: server not configured" \
             "$P_SRV debug_level=3" \
             "$P_CLI debug_level=3 ecjpake_pw=bla \
@@ -5769,7 +5769,7 @@
             -C "found ecjpake_kkpp extension" \
             -s "None of the common ciphersuites is usable"
 
-requires_config_enabled MBEDTLS_KEY_EXCHANGE_ECJPAKE
+requires_config_enabled MBEDTLS_KEY_EXCHANGE_ECJPAKE_ENABLED
 run_test    "ECJPAKE: working, TLS" \
             "$P_SRV debug_level=3 ecjpake_pw=bla" \
             "$P_CLI debug_level=3 ecjpake_pw=bla \