Round up the SSE register save area only if needed

Round up the SSE register save area only if needed

There is is no point to round up the SSE register save area to 16 bytes if
the incoming stack boundary is less than 16 bytes.

	* config/i386/i386.c (ix86_compute_frame_layout): Round up the
	SSE register save area to 16 bytes only if the incoming stack
	boundary is no less than 16 bytes.

From-SVN: r228621