Bluetooth: hci_sock: fix endian bug in hci_sock_setsockopt()

This copies a u16 into the high bits of an int, which works on a big
endian system but not on a little endian system.

Fixes: 09572fca ("Bluetooth: hci_sock: Add support for BT_{SND,RCV}BUF")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>