samsung: add subtarget condition for device

The only device in samsung target is meant to be built with s5pv210
subtarget. Thus, though this won't make a difference for a
one-subtarget target, already add the condition to the Makefile to
make the assignment obvious.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

target/linux/samsung/image/Makefile

@@ -17,6 +17,8 @@ define Device/Default
   DEVICE_DTS = $$(SOC)_$(1)
 endef
 
+ifeq ($(SUBTARGET),s5pv210)
+
 define Device/embedsky_tq210
   DEVICE_VENDOR := EmbedSky
   DEVICE_MODEL := TQ210
@@ -24,4 +26,6 @@ define Device/embedsky_tq210
 endef
 TARGET_DEVICES += embedsky_tq210
 
+endif
+
 $(eval $(call BuildImage))