testsuite: XFAIL ssa-sink-18.c also on powerpc64 [PR111462]

testsuite: XFAIL ssa-sink-18.c also on powerpc64 [PR111462]

powerpc64-linux apparently (not very surprisingly) behaves the same
way as powerpc64le-linux and has 4 sunk statements rather than 5,
so we should xfail it on powerpc64*-*-* rather than just powerpc64le-*-*.
powerpc-linux has 3 sunk statements, but the scan pattern is done for
lp64 only as the comment explains.

2024-02-28  Jakub Jelinek  <jakub@redhat.com>

	PR testsuite/111462
	* gcc.dg/tree-ssa/ssa-sink-18.c: XFAIL also on powerpc64.