rs6000: Delete HAVE_AS_LWSYNC and TARGET_LWSYNC_INSTRUCTION

rs6000: Delete HAVE_AS_LWSYNC and TARGET_LWSYNC_INSTRUCTION

All supported assemblers know lwsync, so we never need to generate this
instruction using the .long escape hatch.

	* config.in (HAVE_AS_LWSYNC): Delete.
	* config/powerpcspe/powerpcspe.h (TARGET_LWSYNC_INSTRUCTION): Delete.
	* config/powerpcspe/sync.md (*lwsync): Always generate lwsync, never
	do it as a .long .
	* config/rs6000/rs6000.h (TARGET_LWSYNC_INSTRUCTION): Delete.
	* config/rs6000/sync.md (*lwsync): Always generate lwsync, never do it
	as a .long .
	* configure.ac: Delete HAVE_AS_LWSYNC.
	* configure: Regenerate.

From-SVN: r264702