Bluetooth: mgmt: Remove leftover queuing of power_off work

Queuing of power_off work was introduced in these functions with commits
8b064a3a ("Bluetooth: Clean up HCI state when doing power off") and
c9910d0f ("Bluetooth: Fix disconnecting connections in non-connected
states") in an effort to clean up state and do things like disconnecting
devices before actually powering off the device.

After that, commit a3172b7e ("Bluetooth: Add timer to force power off")
introduced a timeout to ensure that the device actually got powered off,
even if some of the cleanup work would never complete.

This code later got refactored with commit cf75ad8b ("Bluetooth:
hci_sync: Convert MGMT_SET_POWERED"), which made powering off the device
synchronous and removed the need for initiating the power_off work from
other places. The timeout mentioned above got removed too, because we now
also made use of the command timeout during power on/off.

These days the power_off work still exists, but it only seems to only be
used for HCI_AUTO_OFF functionality, which is why we never noticed
those two leftover places where we queue power_off work. So let's remove
that code.

Fixes: cf75ad8b ("Bluetooth: hci_sync: Convert MGMT_SET_POWERED")
Signed-off-by: Jonas Dreßler <verdre@v0yd.nl>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>