CVE-2021-46969

In the Linux kernel, the following vulnerability has been resolved: bus:
mhi: core: Fix invalid error returning in mhi_queue mhi_queue returns an
error when the doorbell is not accessible in the current state. This can
happen when the device is in non M0 state, like M3, and needs to be
waken-up prior ringing the DB. This case is managed earlier by triggering
an asynchronous M3 exit via controller resume/suspend callbacks, that in
turn will cause M0 transition and DB update. So, since it’s not an error
but just delaying of doorbell update, there is no reason to return an
error. This also fixes a use after free error for skb case, indeed a caller
queuing skb will try to free the skb if the queueing fails, but in that
case queueing has been done.