testsuite: Add appropriate target requirements to P9 testcases.

testsuite: Add appropriate target requirements to P9 testcases.

This patch adds effective target and target specific expected results
to a few P9 testcases.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/builtins-5-p9-runnable.c: Require lp64.
	* gcc.target/powerpc/builtins-msum-runnable.c: Require int128.
	* gcc.target/powerpc/float128-cmp2-runnable.c: Require float128.
	* gcc.target/powerpc/fold-vec-extract-double.p9.c: Require lp64.