media: sti/c8sectpfe: set correct return code

Fixes this smatch warning:

drivers/media/platform/sti/c8sectpfe/c8sectpfe-core.c:829 c8sectpfe_probe() warn: missing error code 'ret'

Set ret to -EINVAL if the reset gpio was not found.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>