drm/vc4: drv: Disable the CRTC at boot time

In order to prevent issues during the firmware to KMS transition, we need
to make sure the pixelvalve are disabled at boot time so that the DRM state
matches the hardware state.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Tested-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/ad57f1bdeae7a99631713b0fc193c86f223de042.1599120059.git-series.maxime@cerno.tech