media: rockchip: rkisp1: remove useless debugfs checks

The debugfs_create_dir() function never returns NULLs so this code will
never be executed.  It's not intended that callers will check for
debugfs errors in the normal case and it's not necessary in this driver,
so we can just delete this code.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>