drm/bridge: sii902x: Add missing \n to the end of some dev_err messages

Trivial fix.
Some dev_err messages in this driver are missing \n, so add them.

Signed-off-by: Liu Ying <gnuiyl@gmail.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1491877339-19913-1-git-send-email-gnuiyl@gmail.com