tests: Add mbedtls_test_ prefix to hexcmp()

Add mbedtls_test_ prefix to hexcmp() test helper
function.

Command to change *.function files:
find . -name "*.function" -exec awk -i inplace \
    '{sub(/hexcmp\>/,"mbedtls_test_&")}1' {} \;

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/tests/suites/test_suite_ecp.function b/tests/suites/test_suite_ecp.function
index 850b77c..e37a017 100644
--- a/tests/suites/test_suite_ecp.function
+++ b/tests/suites/test_suite_ecp.function
@@ -756,7 +756,7 @@
 
     if( ret == 0 )
     {
-        TEST_ASSERT( hexcmp( buf, out->x, olen, out->len ) == 0 );
+        TEST_ASSERT( mbedtls_test_hexcmp( buf, out->x, olen, out->len ) == 0 );
     }
 
 exit: