orion: Set appropriate DEVICE_TYPE for harddisk target

The harddisk target is for NAS boxes, so set the DEVICE_TYPE accordingly so we
get a sensible default package selection.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

target/linux/orion/harddisk/target.mk

@@ -7,6 +7,7 @@
 
 BOARDNAME:=Internal Hard-Disk
 FEATURES+=targz
+DEVICE_TYPE:=nas
 
 define Target/Description
 	Build firmware images for Marvell Orion based boards that boot directly from internal disk storage.