rsi: add hci detach for hibernation and poweroff

As we missed to detach HCI, while entering power off or hibernation,
an extra hci interface gets created whenever system is woken up, to
avoid this we added hci_detach() in rsi_disconnect(), rsi_freeze(),
and rsi_shutdown() functions which are invoked for these tests.
This patch fixes the issue

Signed-off-by: Siva Rebbagondla <siva.rebbagondla@redpinesignals.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>