omni: add back ro.omni.device property

OpenDelta needs it

Change-Id: I0b3c9494a063a7f9d86b845ff3f4467bc1ada744
diff --git a/config/version.mk b/config/version.mk
index 2551d84..044fb0b 100644
--- a/config/version.mk
+++ b/config/version.mk
@@ -27,4 +27,5 @@
 # Apply it to build.prop
 PRODUCT_PRODUCT_PROPERTIES += \
     ro.modversion=OmniROM-$(ROM_VERSION) \
-    ro.omni.version=$(ROM_VERSION)
+    ro.omni.version=$(ROM_VERSION) \
+    ro.omni.device=$(TARGET_PRODUCT_SHORT)