drm/vc4: crtc: Split CRTC data in two

The vc4_crtc_data structure is currently storing data related to both the
general CRTC information needed by the rest of the vc4 driver (like HVS
output and available FIFOs) and some related to the pixelvalve attached to
that CRTC. Let's split this into two structures so that we can reuse the
CRTC part into the TXP later on.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/8eb317c91ac208d7f926d76ad421002fa0364c47.1591882579.git-series.maxime@cerno.tech