[media] saa7134: Fix strange kconfig dependency on RC_CORE

As the code in saa7134-input is not a module, but the config for it is
set as a boolean instead of a tristate, this causes a strange dependency
on RC_CORE.

VIDEO_SAA7134_RC (which determines if saa7134-input.o is built) depends
on RC_CORE and VIDEO_SAA7134. If VIDEO_SAA7134 is compiled as 'y' but
RC_CORE is compiled as 'm' VIDEO_SAA7134_RC can still be set to 'y'
which causes undefined symbols that it needs from RC_CORE.

The simplest solution is to not allow VIDEO_SAA7134_RC be enabled if
RC_CORE compiled as a module (m) and VIDEO_SA7134 is compiled into the
kernel (y).

Suggested-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Cc: Michal Marek <mmarek@suse.cz>
Cc: linux-kbuild <linux-kbuild@vger.kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>