drm/hisilicon: Delete unused local parameters

delete unused variable ‘priv’ to avoid warning.

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/1607339778-20460-3-git-send-email-tiantao6@hisilicon.com