arc: Remove Rcw constraint

arc: Remove Rcw constraint

gcc/Changelog:

	* config/arc/arc.md (smaxsi3): Remove Rcw.
	(sminsi3): Likewise.
	(addsi3_mixed): Likewise.
	(add_f_2): Likewise.
	(subsi3_insn): Likewise.
	(sub_f): Likewise.
	(sub_n): Likewise.
	(bset): Likewise.
	(bxor): Likewise.
	(bclr): Likewise.
	(bset_insn): Likewise.
	(bxor_insn): Likewise.
	(bclr_insn): Likewise.
	(bmsk_insn): Likewise.
	(bicsi3_insn): Likewise.
	(xorsi3): Likewise.
	(negsi2): Likewise.
	(lshrsi3_insn): Likewise.
	(abssf2): Likewise.
	(negsf2): Likewise.
	* config/arc/constraints.md(Rcw): Remove it.

Signed-off-by: Claudiu Zissulescu <claziss@gmail.com>