[media] siano: fix build with allmodconfig

As reported by Stephen:

        After merging the v4l-dvb tree, today's linux-next build (x86_64
        allmodconfig) failed like this:

        ERROR: "sms_ir_exit" [drivers/media/common/siano/smsmdtv.ko] undefined!
        ERROR: "sms_ir_event" [drivers/media/common/siano/smsmdtv.ko] undefined!
        ERROR: "sms_ir_init" [drivers/media/common/siano/smsmdtv.ko] undefined!

The smsir file should be part of the smsmdtv core, if RC is defined.
Fix it.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>