[ARC] Update sleep builtin.

gcc/
2018-04-23  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/arc-protos.h (check_if_valid_sleep_operand): Remove.
	* config/arc/arc.c (arc_expand_builtin): Sleep accepts registers
	and short u6 immediate.
	(check_if_valid_sleep_operand): Remove.
	* config/arc/arc.md (Sleep): Accepts registers and u6 immediates.

changelog

From-SVN: r259557