drm/hisilicon: Features to support reading resolutions from EDID

Use drm_get_edid to get the resolution, if that fails, set it to
a fixed resolution. Rewrite the desrtoy callback function to release
resources.

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/1600778670-60370-3-git-send-email-tiantao6@hisilicon.com