[PATCH v2] firmware/sysfb: Fix device reference count leak in sysfb_disable()

[Wentao Liang]

Hi Thomas, Alex,

Sorry for the very late reply, and thanks for the review.

Alex, you asked whether sysfb_unregister() would still need to be called
when the parent device lookup returns an error. It does: without a known
parent we cannot tell whether the system framebuffer belongs to the
calling device, and leaving it registered could make sysfb interfere with
the native driver. Thomas, that is the defensive behaviour you suggested,
so v2 unregisters unconditionally when sysfb_parent_dev() fails and only
drops the reference on the non-error path.

The reference leak fix itself is unchanged.