drm/i915: Fix crtc nv12 etc. plane bitmasks for DPMS off

drm/i915: Fix crtc nv12 etc. plane bitmasks for DPMS off

We only consider crtc_state->enable when initially calculating plane
visibility. Later on we try to override the plane's state to invisible
if the crtc is in DPMS off state (crtc_state->active==false).
Unfortunately the code doing that only updates the plane_state.visible
flag and the crtc_state.active_planes bimask, but forgets to update
some of the other plane bitmasks stored in the crtc_state. Namely
crtc_state.nv12_planes is left set up based on the original visibility
check which makes icl_check_nv12_planes() pick a slave plane for the
flagged plane in the bitmask. Later on we hit the watermark code
which sees a plane with a slave assigned and it then makes the
logical assumption that the master plane must itself be visible.
Since the master's plane_state.visible flag was already cleared
we get a WARN.

Fix the problem by clearing all the plane bitmasks for DPMS off.
This is more or less the wrong approach and instead we should
calculate all the plane related state purely based crtc_state->enable
(to guarantee that the subsequent DPMS on can't fail). However in
the past we definitely had some roadblocks to making that happen.
Not sure how many are left these days, but let's stick to the current
approach since it's a much simpler fix to the immediate problem
(the WARN).

v2: Keep the visible=false, it's important (Rodrigo)

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200318174515.31637-1-ville.syrjala@linux.intel.com
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>