m7: Define cache image params

Change-Id: I77a4d3750a766d400f98ddc1bf713768adb62df8
diff --git a/BoardConfig.mk b/BoardConfig.mk
index 5243f8b..fa6a387 100644
--- a/BoardConfig.mk
+++ b/BoardConfig.mk
@@ -36,6 +36,8 @@
 # Filesystem
 BOARD_SYSTEMIMAGE_PARTITION_SIZE := 1946156032
 BOARD_USERDATAIMAGE_PARTITION_SIZE := 27917287424
+BOARD_CACHEIMAGE_PARTITION_SIZE := 671088128
+BOARD_CACHEIMAGE_FILE_SYSTEM_TYPE := ext4
 
 # cat /proc/emmc:
 # dev:        size     erasesize name