rs6000 - add speculation_barrier pattern

rs6000 - add speculation_barrier pattern

This patch reworks the existing rs6000_speculation_barrier pattern to
work with the new __builtin_sepculation_safe_value() intrinsic.  The
change is trivial as it simply requires renaming the existing speculation
barrier pattern.

So the total patch is to delete 14 characters!

	* config/rs6000/rs6000.md (speculation_barrier): Renamed from
	rs6000_speculation_barrier.
	* config/rs6000/rs6000.c (rs6000_expand_builtin): Adjust for
	new barrier pattern name.

From-SVN: r263197