Remove internal function md_process()

It was already marked as internal use only, and no longer used
internally. Also, it won't work when we dispatch to PSA.

Remove it before the MD_LIGHT split to avoid a corner case: it's
technically a hashing function, no HMAC or extra metadata, but we still
don't want it in MD_LIGHT really.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/tests/suites/test_suite_md.data b/tests/suites/test_suite_md.data
index 5659ff4..79b8376 100644
--- a/tests/suites/test_suite_md.data
+++ b/tests/suites/test_suite_md.data
@@ -1,6 +1,6 @@
 # Tests of the generic message digest interface
-MD process
-mbedtls_md_process:
+MD list
+mbedtls_md_list:
 
 MD NULL/uninitialised arguments
 md_null_args: