rs6000: testsuite: Fix vec-adde[c]-int128.c

rs6000: testsuite: Fix vec-adde[c]-int128.c

These are a runtime testcases so they should test p8vector_hw instead of
powerpc_p8vector_ok, or they will fail with an illegal instruction on
older processors.

Also they run on any PowerPC, not with just those compilers that were
configured to default to 64-bit targets.

gcc/testsuite/
	* gcc.target/powerpc/vec-adde-int128.c: Use p8vector_hw instead of
	powerpc_p8vector_ok.
	* gcc.target/powerpc/vec-addec-int128.c: Ditto.

From-SVN: r245395