media: seco-cec: fix building with RC_CORE=m

I previously added an RC_CORE dependency here, but missed the corner
case of CONFIG_VIDEO_SECO_CEC=y with CONFIG_RC_CORE=m, which still
causes a link error:

drivers/media/platform/seco-cec/seco-cec.o: In function `secocec_probe':
seco-cec.c:(.text+0x1b8): undefined reference to `devm_rc_allocate_device'
seco-cec.c:(.text+0x2e8): undefined reference to `devm_rc_register_device'
drivers/media/platform/seco-cec/seco-cec.o: In function `secocec_irq_handler':
seco-cec.c:(.text+0xa2c): undefined reference to `rc_keydown'

Refine the dependency to disallow building the RC subdriver in this case.
This is the same logic we apply in other drivers like it.

Fixes: f27dd0ad

 ("media: seco-cec: fix RC_CORE dependency")

Cc: <stable@vger.kernel.org> # 5.1
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>