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_mpi.function b/tests/suites/test_suite_mpi.function
index f2702f1..e7c1f5f 100644
--- a/tests/suites/test_suite_mpi.function
+++ b/tests/suites/test_suite_mpi.function
@@ -354,7 +354,7 @@
     if( result == 0)
     {
 
-        TEST_ASSERT( hexcmp( buf, input_A->x, buflen, input_A->len ) == 0 );
+        TEST_ASSERT( mbedtls_test_hexcmp( buf, input_A->x, buflen, input_A->len ) == 0 );
     }
 
 exit:
@@ -388,7 +388,7 @@
         TEST_ASSERT( mbedtls_mpi_write_binary( &X, buf, buflen ) == 0 );
 
 
-        TEST_ASSERT( hexcmp( buf, input_A->x, buflen, input_A->len ) == 0 );
+        TEST_ASSERT( mbedtls_test_hexcmp( buf, input_A->x, buflen, input_A->len ) == 0 );
     }
 
 exit: