drm/vc4: kms: Assign a FIFO to enabled CRTCs instead of active

The HVS has three FIFOs that can be assigned to a number of PixelValves
through a mux.

However, changing that FIFO requires that we disable and then enable the
pixelvalve, so we want to assign FIFOs to all the enabled CRTCs, and not
just the active ones.

Fixes: 87ebcd4 ("drm/vc4: crtc: Assign output to channel automatically")
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Tested-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200918145918.101068-1-maxime@cerno.tech

Author: mripard

drivers/gpu/drm/vc4/vc4_kms.c

@@ -643,7 +643,7 @@ vc4_atomic_check(struct drm_device *dev, struct drm_atomic_state *state)
 		struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
 		unsigned int matching_channels;
 
-		if (!crtc_state->active)
+		if (!crtc_state->enable)
 			continue;
 
 		/*