drm: bridge: it66121: Don't use DDC error IRQs

The DDC error IRQs will fire on the IT6610 every time the FIFO is empty,
which is not very helpful. To resolve this, we can simply disable them,
and handle DDC errors in it66121_wait_ddc_ready().

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221214125821.12489-7-paul@crapouillou.net