drm/i915: enable IPS for bpp <= 24

Art confirms that this should work fine.  Since most panels are 18bpp
with dithering from 24bpp, the existing code wouldn't be enabled in most
cases.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -4091,7 +4091,7 @@ static void hsw_compute_ips_config(struct intel_crtc *crtc,
 {
 	pipe_config->ips_enabled = i915_enable_ips &&
 				   hsw_crtc_supports_ips(crtc) &&
-				   pipe_config->pipe_bpp == 24;
+				   pipe_config->pipe_bpp <= 24;
 }
 
 static int intel_crtc_compute_config(struct intel_crtc *crtc,