[media] em28xx: add missing auto-selections for build

With MEDIA_SUBDRV_AUTOSELECT enabled in the kernel config, the em28xx
driver currently does't select some used subdrivers.
Fix this by adding the missing auto-selections to the Kconfig file.

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>