Remove dead code from graphite-optimize-isl.c

Remove dead code from graphite-optimize-isl.c

The variable `static bool enable_polly_vector' is always assigned to false.
This results in dead code in optimize-isl.c.  No functional change intended.

Passes bootstrap and regtest.

gcc/ChangeLog:

2015-09-11  Aditya Kumar  <aditya.k7@samsung.com>

	* graphite-optimize-isl.c (disable_tiling): Remove.
	(get_schedule_for_band): Do not use disable_tiling.
	(get_prevector_map): Delete function.
	(enable_polly_vector): Remove.
	(get_schedule_for_band_list): Remove dead code.

From-SVN: r227696