drm/bridge: it6505: fix HDCP CTS KSV list read with UNIGRAF DPR-100.

When running the HDCP CTS test with UNIGRAF DPR-100.
KSV list must be read from DP_AUX_HDCP_KSV_FIFO in an AUX request,
and can not separate with multiple read requests.

The AUX operation command "CMD_AUX_GET_KSV_LIST" reads the KSV list
with AUX FIFO and is able to read DP_AUX_HDCP_KSV_FIFO in an AUX request.

Add it6505_get_ksvlist() which uses CMD_AUX_GET_KSV_LIST operation
to read the KSV list.

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-v7-7-e0fdd4844703@ite.corp-partner.google.com