* config/mips/mips.h (MIPS_STACK_ALIGN): Implement using
	ROUND_UP macro.
	* config/mips/mips.c (mips_setup_incoming_varargs): Use
	ROUND_DOWN to calculate off.
	(mips_gimplify_va_arg_expr): Use ROUND_UP to calculate rsize.
	(mips_emit_probe_stack_range): Use ROUND_DOWN to calculate
	rounded_size.

From-SVN: r228829