Fix the check for max CA intermediates in ssl-opt.sh

The tests only work for a specific number for MBEDTLS_X509_MAX_INTERMEDIATE_CA
so the check has been changed to confirm the default value, and to show an error
otherwise.
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 92acd4e..280fc63 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -2106,22 +2106,17 @@
 # The "max_int chain" tests assume that MAX_INTERMEDIATE_CA is set to its
 # default value (8)
 
-: ${MAX_IM_CA:='19'}
+MAX_IM_CA='8'
 MAX_IM_CA_CONFIG=$( ../scripts/config.pl get MBEDTLS_X509_MAX_INTERMEDIATE_CA)
 
-if [ -n "$MAX_IM_CA_CONFIG" ] && [ "$MAX_IM_CA_CONFIG" -gt "$MAX_IM_CA" ]; then
+if [ -n "$MAX_IM_CA_CONFIG" ] && [ "$MAX_IM_CA_CONFIG" -ne "$MAX_IM_CA" ]; then
     printf "The ${CONFIG_H} file contains a value for the configuration of\n"
-    printf "MBEDTLS_X509_MAX_INTERMEDIATE_CA that is greater than the script’s\n"
+    printf "MBEDTLS_X509_MAX_INTERMEDIATE_CA that is different from the script’s\n"
     printf "test value of ${MAX_IM_CA}. \n"
     printf "\n"
-    printf "By default, this value cannot be higher as there are insufficient\n"
-    printf "test certificate files available to test with.\n"
+    printf "The tests assume this value and if it changes, the tests in this\n"
+    printf "script should also be adjusted.\n"
     printf "\n"
-    printf "To generate additional test certificates use the script:\n"
-    printf "   tests/data_files/dir-maxpath/long.sh\n"
-    printf "\n"
-    printf "To test using an alternative value, please set the environment variable\n"
-    printf "MAX_IM_CA or change the default value in the script tests/ssl-opt.sh.\n"
 
     exit 1
 fi