mbedtls: Re-add patch to disable VIA padlock

The comment mentioned a conflict with libwebsockets, but we actually
still get this conflict even now that we don't use libwebsockets.
Not sure what component is clashing but we should basically just keep
this patch.

Follow-up to #36823.

(cherry picked from commit 8189abd)

Note: For the 3.1 branch, only modifies the README.md a bit as I had
kept the patch removed in master/3.2.

thirdparty/README.md

@@ -295,9 +295,9 @@ File extracted from upstream release tarball (`-apache.tgz` variant):
 - LICENSE and apache-2.0.txt files
 - Applied the patch in `thirdparty/mbedtls/patches/1453.diff` (PR 1453).
   Soon to be merged upstream. Check it out at next update.
-- Applied the patch in `thirdparty/mbedtls/patches/padlock.diff`. This disables VIA
-  padlock support which defines a symbol `unsupported` which clashes with
-  a symbol in libwebsockets.
+- Applied the patch in `thirdparty/mbedtls/patches/padlock.diff`. This disables
+  VIA padlock support which defines a symbol `unsupported` which clashes with
+  a pre-defined symbol.
 
 
 ## miniupnpc