drm/imx/dcss: fix coccinelle warning

This small patch fixes a warning that I got while running coccinelle:

  CHECK   drivers/gpu/drm/imx/dcss/dcss-plane.c
  drivers/gpu/drm/imx/dcss/dcss-plane.c:107:21-23: WARNING !A || A && B is equivalent to !A || B

Fixes: 9021c317

 ("drm/imx: Add initial support for DCSS on iMX8MQ")
Signed-off-by: Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20201105140127.25249-3-laurentiu.palcu@oss.nxp.com