drm/hisilicon/hibmc: add dp aux in hibmc drivers

Add dp aux read/write functions. They are basic functions
and will be used later.

Signed-off-by: Baihan Li <libaihan@huawei.com>
Signed-off-by: Yongbang Shi <shiyongbang@huawei.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Tian Tao <tiantao6@hisilicon.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250103093824.1963816-2-shiyongbang@huawei.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>