Bluetooth: hci_qca: Add QCA Rome power off support to the qca_power_shutdown()

Current qca_power_shutdown() only supports wcn399x, this patch adds Rome
power off support to it. For Rome it just needs to pull down the bt_en
GPIO to power off it. This patch also replaces all the power off operation
in qca_close() with the unified qca_power_shutdown() call.

Signed-off-by: Rocky Liao <rjliao@codeaurora.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>