gpgconf: Fix validity check for UINT32 values.

* tools/gpgconf-comp.c (option_check_validity): Enable check for
UINT32.

This is actually a bug which inhibited the checking of values of type
UINT32.

(cherry picked from commit 3f6abb57a7b5e54b593c5775c8f7a07d61119705)

• Reported-by: Günther Noack <gnoack@google.com>
• Signed-off-by: Werner Koch <wk@gnupg.org>