rs6000: Fix compiler warning

2014-11-20  Markus Trippelsdorf  <markus@trippelsdorf.de>

	* config/rs6000/rs6000.c (includes_rldic_lshift_p): Use
	HOST_WIDE_INT_M1U instead of ~0.
	(includes_rldicr_lshift_p): Likewise.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@217905 138bc75d-0d04-0410-961f-82ee72b054a4