arm: Fix canary address calculation for non-PIC

arm: Fix canary address calculation for non-PIC

For non-PIC, the stack protector patterns did:

	  rtx mem = XEXP (force_const_mem (SImode, operands[1]), 0);
	  emit_move_insn (operands[2], mem);

Here, operands[1] is the address of the canary (&__stack_chk_guard)
and operands[2] is the register that we want to move that address into.
However, the code above instead sets operands[2] to the address of a
constant pool entry that contains &__stack_chk_guard, rather than to
&__stack_chk_guard itself.  The sequence therefore does one less
pointer indirection than it should.

The net effect was to use &__stack_chk_guard for stack-smash detection,
instead of using __stack_chk_guard itself.

gcc/
	* config/arm/arm.md (*stack_protect_combined_set_insn): For non-PIC,
	load the address of the canary rather than the address of the
	constant pool entry that points to it.
	(*stack_protect_combined_test_insn): Likewise.

gcc/testsuite/
	* gcc.target/arm/stack-protector-3.c: New test.
	* gcc.target/arm/stack-protector-4.c: Likewise.