Bluetooth: MGMT: Fix status of pending commands flushed on power off

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: MGMT: Fix status of pending commands flushed on power off

cmd_complete_rsp() receives a struct cmd_lookup and, for a pending
command that has no cmd_complete callback, falls through to
cmd_status_rsp(cmd, data). cmd_status_rsp() reads data as a u8 *, so
the status sent comes from the first byte of match->sk's
representation, not from match->mgmt_status.

commit f53e1c9c726d ("Bluetooth: MGMT: Fix possible crash on
mgmt_index_removed") changed the callers' data from &status to &match
and updated the cmd_complete branch to match->mgmt_status, but left
the fall-through passing data unchanged.

In mgmt_index_removed() match->sk is NULL, so every such command is
answered with status 0x00 (Success) instead of
MGMT_STATUS_INVALID_INDEX. In __mgmt_power_off() it is NULL too,
unless a Set Powered command was pending: then settings_rsp() has
stored that command's socket in match->sk, and the byte sent comes
from the socket pointer. Either way the status the caller set,
MGMT_STATUS_NOT_POWERED (or MGMT_STATUS_INVALID_INDEX when the device
is being unregistered), is lost.

Pass the status the callers set.

This was seen on a QCA9377 laptop: bluetoothd's Start Discovery,
pending when the adapter was powered off, was answered with Command
Status 0x00 and no parameters, and bluetoothd 5.72 crashed on the
zero-length success. BlueZ master has since added the length check
on that path ("adapter: Fix crash on short start discovery reply",
BlueZ a734b06059cb), but userspace should still be told Not Powered,
not Success.

Tested on Ubuntu 7.0.0-31 with a virtual controller (hci_vhci):
power off is held in HCI Write Scan Enable while a Start Discovery is
submitted, and the flush answers it with status 0x00 before this
change and 0x0f (Not Powered) after.