sna: Return early if the Drawable box exactly matches one CRTC

If we are trying to find the best coverage, then by definition if the
drawable is an exact match for one CRTC, we can stop looking.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

src/sna/sna_display.c

@@ -2739,6 +2739,11 @@ sna_covering_crtc(ScrnInfoPtr scrn,
 		     __FUNCTION__, c,
 		     crtc->bounds.x1, crtc->bounds.y1,
 		     crtc->bounds.x2, crtc->bounds.y2));
+		if (*(const uint64_t *)box == *(uint64_t *)&crtc->bounds) {
+			DBG(("%s: box exactly matches crtc [%d]\n",
+			     __FUNCTION__, c));
+			return crtc;
+		}
 
 		if (!sna_box_intersect(&cover_box, &crtc->bounds, box))
 			continue;