uqmi: add support of using device symlinks.

It's useful when using multiple usb devices that should be bound to
certain usb ports. Symlinks are created by hotplug handlers.

Signed-off-by: Nickolay Ledovskikh <nledovskikh@gmail.com>

package/network/utils/uqmi/files/lib/netifd/proto/qmi.sh

@@ -42,6 +42,8 @@ proto_qmi_setup() {
 		proto_set_available "$interface" 0
 		return 1
 	}
+
+	device="$(readlink -f $device)"
 	[ -c "$device" ] || {
 		echo "The specified control device does not exist"
 		proto_notify_error "$interface" NO_DEVICE