media: rcar-csi2: Fix coccinelle warning for PTR_ERR_OR_ZERO()

Use the PTR_ERR_OR_ZERO() macro instead of construct:

    if (IS_ERR(foo))
        return PTR_ERR(foo);

    return 0;

Fixes: 3ae854cafd76 ("rcar-csi2: Use standby mode instead of resetting")

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Ulrich Hecht <uli+renesas@fpond.eu>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>