Fix ARM ICE for register var asm ("pc") (PR target/60606).

Fix ARM ICE for register var asm ("pc") (PR target/60606).

	PR target/60606
	PR target/61330
	* varasm.c (make_decl_rtl): Clear DECL_ASSEMBLER_NAME and
	DECL_HARD_REGISTER and return for invalid register specifications.
	* cfgexpand.c (expand_one_var): If expand_one_hard_reg_var clears
	DECL_HARD_REGISTER, call expand_one_error_var.
	* config/arm/arm.c (arm_hard_regno_mode_ok): Do not allow
	CC_REGNUM with non-MODE_CC modes.
	(arm_regno_class): Return NO_REGS for PC_REGNUM.

testsuite:
	* gcc.dg/torture/pr60606-1.c, gcc.target/arm/pr60606-2.c,
	gcc.target/arm/pr60606-3.c, gcc.target/arm/pr60606-4.c: New tests.

From-SVN: r214526