CVE-2023-52731

In the Linux kernel, the following vulnerability has been resolved: fbdev:
Fix invalid page access after closing deferred I/O devices When a fbdev
with deferred I/O is once opened and closed, the dirty pages still remain
queued in the pageref list, and eventually later those may be processed in
the delayed work. This may lead to a corruption of pages, hitting an Oops.
This patch makes sure to cancel the delayed work and clean up the pageref
list at closing the device for addressing the bug. A part of the cleanup
code is factored out as a new helper function that is called from the
common fb_release().