drm/kmb: Fix for build errors with Warray-bounds

This fixes the following build error

drivers/gpu/drm/kmb/kmb_plane.c: In function 'kmb_plane_atomic_disable':
drivers/gpu/drm/kmb/kmb_plane.c:165:34: error: array subscript 3 is above array bounds of 'struct layer_status[2]' [-Werror=array-bounds]
  165 |                 kmb->plane_status[plane_id].ctrl =
  LCD_CTRL_GL2_ENABLE;
  |                 ~~~~~~~~~~~~~~~~~^~~~~~~~~~
  In file included from drivers/gpu/drm/kmb/kmb_plane.c:17:
  drivers/gpu/drm/kmb/kmb_drv.h:61:41: note: while referencing 'plane_status'
  61 |         struct layer_status  plane_status[KMB_MAX_PLANES];
  |                                         ^~~~~~~~~~~~
  drivers/gpu/drm/kmb/kmb_plane.c:162:34: error: array subscript 2 is above array bounds of 'struct layer_status[2]' [-Werror=array-bounds]
  162 |  kmb->plane_status[plane_id].ctrl =  LCD_CTRL_GL1_ENABLE;
  |                 ~~~~~~~~~~~~~~~~~^~~~~~~~~~
  In file included from
  drivers/gpu/drm/kmb/kmb_plane.c:17:
  drivers/gpu/drm/kmb/kmb_drv.h:61:41: note: while referencing 'plane_status'
  61 |         struct layer_status  plane_status[KMB_MAX_PLANES];
  |
  ^~~~~~~~~~~~

Fixes: 7f7b96a8

 ("drm/kmb: Add support for KeemBay Display")
Signed-off-by: Anitha Chrisanthus <anitha.chrisanthus@intel.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220127194227.2213608-1-anitha.chrisanthus@intel.com