Bluetooth: Update and rename mgmt_remove_keys to mgmt_unpair_device

This patch renames the mgmt_remove_keys command to mgmt_unpair_device
and updates its parameters to match the latest API (specifically, it
adds an address type parameter to the command and its response).

Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
Acked-by: Marcel Holtmann <marcel@holtmann.org>