drm/hisilicon: Code refactoring for hibmc_drv_de

The memory used to be allocated with devres helpers and released
automatically. In rare circumstances, the memory's release could
have happened before the DRM device got released, which would have
caused memory corruption of some kind. Now we're embedding the data
structures in struct hibmc_drm_private. The whole release problem
has been resolved, because struct hibmc_drm_private is allocated
with drmm_kzalloc and always released with the DRM device.

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/1597218179-3938-3-git-send-email-tiantao6@hisilicon.com