drm/i915: Disable planes more atomically during modesets

drm/i915: Disable planes more atomically during modesets

Follow in the footsteps of commit c610e841f19d ("drm/i915:
Do plane/etc. updates more atomically across pipes") and
do the plane disables back to back for all pipes also when
we are disabling pipes.

This should provide for a potentially more atomic user
experience, which might be especially nice when using
joiner or tiled displays.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240305084730.19182-3-ville.syrjala@linux.intel.com
Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>