Bluetooth: hci_h5: reset hci_uart::priv in the close() method

Bluetooth: hci_h5: reset hci_uart::priv in the close() method

Unlike the other HCI UART drivers, the 3-wire UART driver doesn't reset
hci_uart::priv in its close() method -- this shouldn't pose a problem as
all the methods in *struct* hci_uart_proto should only be called after the
open() method that sets up hci_uart::priv properly. However, it seems wise
to be more consistent and provide for the *struct* hci_uart_proto methods
the same state that exists before the first open() method call (so that
they rather crash than dereference a stale hci_uart::priv pointer)...

Found by Linux Verification Center (linuxtesting.org) with the Svace static
analysis tool.

Signed-off-by: Sergey Shtylyov <s.shtylyov@auroraos.dev>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>