[ARC] Remove Rs5 constraint.

[ARC] Remove Rs5 constraint.

New LRA algorithms require the all the register constraints to be
defined using define_register_constraint keyword. However, Rs5
constraint was not LRA proof. Remove it and replace it by equivalent
Rcd constraint.

gcc/
xxxx-xx-xx  Claudiu Zissulescu  <claziss@synopsys.com>

	* config/arc/arc.md (sibcall_insn): Use Rcd constraint.
	(sibcall_value_insn): Likewise.
	* config/arc/constraints.md (Rs5): Remove.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@270386 138bc75d-0d04-0410-961f-82ee72b054a4