linuxkpi: Add same_type and must_be_array macros

The same_type macro simply wraps around builtin_types_compatible_p which
exist for both GCC and CLANG, which returns 1 if both types are the same.
The __must_be_array macros returns 1 if the argument is an array.

This is needed for DRM v5.3

Sponsored-by: The FreeBSD Foundation
Reviewed by: hselasky
Differential Revision: https://reviews.freebsd.org/D24953