The probe function used 'goto out' everywhere, except in one
place where it returned an error. That too should be a 'goto out'.

This fixes a smatch warning:

mmp-driver.c:257 mmpcam_probe() warn: missing unwind goto?
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>