i386: Fix ix86_function_arg_regno_p to return correct SSE regno for 32bit TARGET_MACHO

i386: Fix ix86_function_arg_regno_p to return correct SSE regno for 32bit TARGET_MACHO

Use up to SSE_REGPARM_MAX registers to pass function parameters
for 32bit Mach-O targets.  Also, define X86_32_MMX_REGPARM_MAX
to return 0 for 32bit Mach-O targets.

2020-11-03  Uroš Bizjak  <ubizjak@gmail.com>

gcc/

	* config/i386/i386.c (ix86_function_arg_regno_p): Use up to
	SSE_REGPARM_MAX registers to pass function parameters
	for 32bit Mach-O targets.
	* config/i386/i386.h (X86_32_MMX_REGPARM_MAX): New macro.
	(MMX_REGPARM_MAX): Use it.