rs6000: Remove builtin mask check from builtin_decl [PR102347]

rs6000: Remove builtin mask check from builtin_decl [PR102347]

As the discussion in PR102347, currently builtin_decl is invoked so
early, it's when making up the function_decl for builtin functions,
at that time the rs6000_builtin_mask could be wrong for those
builtins sitting in #pragma/attribute target functions, though it
will be updated properly later when LTO processes all nodes.

This patch is to align with the practice i386 port adopts, also
align with r10-7462 by relaxing builtin mask checking in some places.

gcc/ChangeLog:

	PR target/102347
	* config/rs6000/rs6000-call.c (rs6000_builtin_decl): Remove builtin mask
	check.

gcc/testsuite/ChangeLog:

	PR target/102347
	* gcc.target/powerpc/pr102347.c: New test.