media: Kconfig: allow to select drivers if EMBEDDED

Embedded systems often connect to sensors or other multimedia
subdevices directly. Currently, to be able to select such a
subdevice (e.g. CONFIG_VIDEO_OV5640) disabling of the auto-
select config option is needed (CONFIG_MEDIA_SUBDRV_AUTOSELECT).

This is inconvenient as the ancillary drivers for a particular
device then need to be selected manually.

Allow to select drivers manually while keeping the auto-select
feature in case EXPERT (selected by EMBEDDED) is enabled.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>