[ARC] Update mode_dependent_address_p hook.

Update arc_mode_dependent_address_p to avoid emitting subreg(mem (reg
..)) when expanding by relaxing the conditions.

gcc/
2017-04-14  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/arc.c (arc_mode_dependent_address_p): Relax
	conditions to take advantage of various optimizations.

From-SVN: r246925