drm/hisilicon/hibmc: Add dp serdes cfg in dp process

drm/hisilicon/hibmc: Add dp serdes cfg in dp process

Add dp serdes cfg in link training process, and related adapting
and modificating. Change some init values about training, because we want
completely to negotiation process, so we start with the maximum rate and
the electrical characteristic level is 0. Because serdes default cfgs is
changed and used in hibmc_kms_init(), we changed the if-statement to check
whether the value is 0.

Signed-off-by: Baihan Li <libaihan@huawei.com>
Signed-off-by: Yongbang Shi <shiyongbang@huawei.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20250331074212.3370287-4-shiyongbang@huawei.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>