rs6000: Add tests for SSE4.1 "ceil" intrinsics

rs6000: Add tests for SSE4.1 "ceil" intrinsics

Add the tests for _mm_ceil_pd, _mm_ceil_ps, _mm_ceil_sd, _mm_ceil_ss.

Copy a test for _mm_ceil_pd and _mm_ceil_ps from
gcc/testsuite/gcc.target/i386.

Define __VSX_SSE2__ to pick up some union definitions in
m128-check.h.

2021-07-30  Paul A. Clarke  <pc@us.ibm.com>

gcc/testsuite
	* gcc.target/powerpc/sse4_1-ceilpd.c: New.
	* gcc.target/powerpc/sse4_1-ceilps.c: New.
	* gcc.target/powerpc/sse4_1-ceilsd.c: New.
	* gcc.target/powerpc/sse4_1-ceilss.c: New.
	* gcc.target/powerpc/sse4_1-round-data.h: New.
	* gcc.target/powerpc/sse4_1-round.h: New.
	* gcc.target/powerpc/sse4_1-round2.h: New.
	* gcc.target/powerpc/sse4_1-roundpd-3.c: Copy from gcc.target/i386
	and adjust dg directives to suit.
	* gcc.target/powerpc/sse4_1-check.h (__VSX_SSE2__): Define.