device: Fix dotted vlan interface staying down

device: Fix dotted vlan interface staying down

Using the config below a dotted vlan interface stays down as get_vlan_device
does not find the device due to the aliased device stacked on top of the base
device.
As all devices; aliased devices being the exception; are in the device list
use device_find to find the device when setting the link state

config interface 'test'
    option proto 'static'
    option ipaddr '192.168.2.1'
    option netmask '255.255.255.0'

config interface 'test2'
    option ifname '@test.1'
    option proto 'dhcp'

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>