media: au0828: fix RC_CORE dependency

When RC_CORE is a loadable module, and au0828 is built-in including
the RC support, we get a link error:

drivers/media/usb/au0828/au0828-input.o: In function `au0828_get_key_au8522':
au0828-input.c:(.text+0x474): undefined reference to `ir_raw_event_store'
drivers/media/usb/au0828/au0828-input.o: In function `au0828_rc_register':
au0828-input.c:(.text+0x7c8): undefined reference to `rc_allocate_device'
au0828-input.c:(.text+0x8f8): undefined reference to `rc_register_device'

This adds an additional dependency, similar to the one for em28xx,
to ensure the broken configuration is never used.

Fixes: 2fcfd317 ("[media] au0828: add support for IR on HVR-950Q")

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>