drm/bridge: it6505: Change definition of AUX_FIFO_MAX_SIZE

drm/bridge: it6505: Change definition of AUX_FIFO_MAX_SIZE

The hardware AUX FIFO is 16 bytes
Change definition of AUX_FIFO_MAX_SIZE to 16

Fixes: b5c84a9edcd4 ("drm/bridge: add it6505 driver")
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Hermes Wu <hermes.wu@ite.com.tw>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20241230-v7-upstream-v7-1-e0fdd4844703@ite.corp-partner.google.com