drm/bridge: it6505: Add range and selector_reg

There are 2 banks on it6505, and when writing to different bank,
REG_BANK_SEL needs to be set to the targeted bank. The current code set
this additionally, which causes a race condition when a process is
writing bank 0 registers while another process set the bank to 1. Set
ranges in regmap config so the regmap API would handle the bank changes.

Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230327044804.3657551-1-hsinyi@chromium.org