drm/bridge: sil_sii8620: do not have a dependency of RC_CORE

This patch makes RC_CORE to be selected with this driver.

sil_sii8620 driver calls remote controller interfaces directly
so RC_CORE should be enabled mandatorily.

And some boards not using remote controller device don't really
need to know that RC_CORE config should be enabled to use sil_sii8620
driver only for HDMI.

Changelog v2:
- select INPUT because compiling will fail without INPUT.

Signed-off-by: Inki Dae <inki.dae@samsung.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1527154379-31886-1-git-send-email-inki.dae@samsung.com