[explow] PR target/85173: validize memory before passing it on to target probe_stack

[explow] PR target/85173: validize memory before passing it on to target probe_stack

In this PR the expansion code emits an invalid memory address for the stack probe, which the backend fails to recognise.
The address is created explicitly in anti_adjust_stack_and_probe_stack_clash in explow.c and passed down to gen_probe_stack
without any validation in emit_stack_probe.

This patch fixes the ICE by calling validize_mem on the memory location before passing it down to the target.
Jakub pointed out that we also want to create valid addresses for the probe_stack_address case, so this patch
creates an expand operand and legitimizes it before passing it down to the probe_stack_address expander.

This patch passes bootstrap and testing on arm-none-linux-gnueabihf and aarch64-none-linux-gnu
and ppc64le-redhat-linux on gcc112 in the compile farm.

	PR target/85173
	* explow.c (emit_stack_probe): Call validize_mem on memory location
	before passing it to gen_probe_stack.  Create address operand and
	legitimize it for the probe_stack_address case.

	* gcc.target/arm/pr85173.c: New test.

From-SVN: r259266