lxd/instance/drivers/qemu: Remove unused arguments
lxd/instance/drivers/qemu: Remove unused arguments

This removes unused argument from addUSBDeviceConfig. Since USB devices
are now being attached using QMP, there's no need for them anymore.

Signed-off-by: Thomas Hipp <5f82c492b3b00e427412d216ce820707a10c51ce@canonical.com>

stgraber/lxd,stgraber/lxd,hallyn/lxd,lxc/lxd,stgraber/lxd,hallyn/lxd,lxc/lxd,stgraber/lxd,hallyn/lxd,hallyn/lxd,stgraber/lxd,stgraber/lxd,lxc/lxd,hallyn/lxd,lxc/lxd,lxc/lxd,lxc/lxd,stgraber/lxd,hallyn/lxd,lxc/lxd