Bluetooth: vhci: Fix race at creating hci device

Bluetooth: vhci: Fix race at creating hci device

commit c7c999cb18da88a881e10e07f0724ad0bfaff770 upstream.

hci_vhci driver creates a hci device object dynamically upon each
HCI_VENDOR_PKT write.  Although it checks the already created object
and returns an error, it's still racy and may build multiple hci_dev
objects concurrently when parallel writes are performed, as the device
tracks only a single hci_dev object.

This patch introduces a mutex to protect against the concurrent device
creations.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>