Move device specific properties to /vendor

By setting BOARD_PROPERTY_OVERRIDES_SPLIT_ENABLED on marlin and
sailfish the device specific properties like ro.product.board
are hosted in /vendor/build.prop.

Test: build and flash on sailfish and marlin.
Change-Id: If2d22ac8078f904789a5be3ac2db8928d23dec1f
diff --git a/marlin/BoardConfig.mk b/marlin/BoardConfig.mk
index a843099..c6e2a60 100644
--- a/marlin/BoardConfig.mk
+++ b/marlin/BoardConfig.mk
@@ -213,3 +213,5 @@
 
 # Use mke2fs to create ext4 images
 TARGET_USES_MKE2FS := true
+
+BOARD_PROPERTY_OVERRIDES_SPLIT_ENABLED := true
diff --git a/sailfish/BoardConfig.mk b/sailfish/BoardConfig.mk
index 06efeed..b390f9b 100644
--- a/sailfish/BoardConfig.mk
+++ b/sailfish/BoardConfig.mk
@@ -200,3 +200,5 @@
 
 # Testing related defines
 BOARD_PERFSETUP_SCRIPT := platform_testing/scripts/perf-setup/sailin-setup.sh
+
+BOARD_PROPERTY_OVERRIDES_SPLIT_ENABLED := true