[AArch64] Make aarch64_min_divisions_for_recip_mul configurable

[AArch64] Make aarch64_min_divisions_for_recip_mul configurable

On behalf of Wilco Dijkstra

2015-05-01  Wilco Dijkstra  <wdijkstr@arm.com>

	* gcc/config/aarch64/aarch64-protos.h (tune_params):
	Add min_div_recip_mul_sf and min_div_recip_mul_df fields.
	* gcc/config/aarch64/aarch64.c (aarch64_min_divisions_for_recip_mul):
	Return value depending on target.
	(generic_tunings): Initialize new target settings.
	(cortexa53_tunings): Likewise.
	(cortexa57_tunings): Likewise.
	(thunderx_tunings): Likewise.
	(xgene1_tunings): Likewise.

From-SVN: r222679