ft32: Fix up ft32_setup_incoming_varargs [PR114175]

ft32: Fix up ft32_setup_incoming_varargs [PR114175]

Like for x86-64, alpha or rs6000, ft32 seems to be affected too.

Just visually checked differences in c23-stdarg-9.c assembly in a cross
without/with the patch, committed to trunk.

2024-03-20  Jakub Jelinek  <jakub@redhat.com>

	PR target/114175
	* config/ft32/ft32.cc (ft32_setup_incoming_varargs): Only skip
	function arg advance for TYPE_NO_NAMED_ARGS_STDARG_P functions
	if arg.type is NULL.

(cherry picked from commit 22612a8b5e0853c530f98fc7c0d6f6812b36518d)