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

[jhb]

Summary

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.

[imp]

This looks good, but the way to test it is to change printf0 to printf on that one line :)

[jhb]

In D45941#1047201, @imp wrote:

This looks good, but the way to test it is to change printf0 to printf on that one line :)

I just did that test and world and kernel built fine with that change.