devel/freebsd-gcc*: Fix error in printf0 format checker patch

Fix a mismerge of the printf0 format checking patch from GCC 9 to GCC
12/13.  GCC 11 and later don't warn for NULL format strings (instead a
separate nonnull attribute is used).  The printf0 format specifier is
left for now to support builds of existing FreeBSD releases but will
be removed in the future.

Reviewed by:	imp
Differential Revision:	https://reviews.freebsd.org/D45941