drm/bridge: it66121: Initialize {device,vendor}_ids

These two arrays are populated with data read from the I2C device
through regmap_read(), and the data is then compared with hardcoded
vendor/product ID values of supported chips.

However, the return value of regmap_read() was never checked. This is
fine, as long as the two arrays are zero-initialized, so that we don't
compare the vendor/product IDs against whatever garbage is left on the
stack.

Address this issue by zero-initializing these two arrays.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Fixes: 988156dc ("drm: bridge: add it66121 driver")
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210827163956.27517-1-paul@crapouillou.net