drm: Use the state pointer directly in planes atomic_check

Now that atomic_check takes the global atomic state as a parameter, we
don't need to go through the pointer in the plane state.

This was done using the following coccinelle script:

@ plane_atomic_func @
identifier helpers;
identifier func;
@@

static struct drm_plane_helper_funcs helpers = {
	...,
	.atomic_check = func,
	...,
};

@@
identifier plane_atomic_func.func;
identifier plane, state;
identifier plane_state;
@@

  func(struct drm_plane *plane, struct drm_atomic_state *state) {
  ...
- struct drm_plane_state *plane_state = drm_atomic_get_new_plane_state(state, plane);
  <... when != plane_state
- plane_state->state
+ state
  ...>
 }

@@
identifier plane_atomic_func.func;
identifier plane, state;
identifier plane_state;
@@

  func(struct drm_plane *plane, struct drm_atomic_state *state) {
  ...
  struct drm_plane_state *plane_state = drm_atomic_get_new_plane_state(state, plane);
  <...
- plane_state->state
+ state
  ...>
 }

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20210219120032.260676-5-maxime@cerno.tech