drm: bridge: it66121: Write AVI infoframe with regmap_bulk_write()

Since all AVI infoframe registers are contiguous in the address space,
the AVI infoframe can be written in one go with regmap_bulk_write().

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221214125821.12489-5-paul@crapouillou.net