[media] media: i2c: remove duplicate checks for EPERM in dbg_g/s_register

This patch removes check for EPERM in dbg_g/s_register of subdevice
drivers as this check is already performed by core.

Signed-off-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>