Fix loop optimization when ZOL is not available in xtensa configuration

Fix loop optimization when ZOL is not available in xtensa configuration

Currently building gcc for xtensa configuration with XCHAL_HAVE_LOOPS
set to 0 fails with the following error:

  xtensa.c:3952: undefined reference to `reorg_loops(bool, hw_doloop_hooks*)'

Only compile target-specific zero-overhead loop optimization code when
TARGET_LOOPS allows it.

2014-12-30  Max Filippov  <jcmvbkbc@gmail.com>

	* config/xtensa/xtensa.c (hwloop_optimize, hwloop_fail,
	hwloop_pattern_reg, xtensa_doloop_hooks, xtensa_reorg_loops):
	put under #if TARGET_LOOPS guard.

From-SVN: r219206