bpf: Allow verifier to fixup kernel module kfuncs

bpf: Allow verifier to fixup kernel module kfuncs

Allow verifier to fixup kfuncs in kernel module to support kfuncs with
__prog arguments. Currently, special kfuncs and kfuncs with __prog
arguments are kernel kfuncs. Allowing kernel module kfuncs should not
affect existing kfunc fixup as kernel module kfuncs have BTF IDs greater
than kernel kfuncs' BTF IDs.

Signed-off-by: Amery Hung <ameryhung@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20251203233748.668365-2-ameryhung@gmail.com