peregrine: Specify we have a cache partition

* In android 7.1 /cache is symlinked to /data/cache
  -> set BOARD_CACHEIMAGE_FILE_SYSTEM_TYPE to switch to the old "mkdir"

Change-Id: I0c6d410063231a4f2de964b297561d5d2f10fd57

BoardConfig.mk

@@ -37,6 +37,8 @@ BOARD_BOOTIMAGE_PARTITION_SIZE := 10485760
 BOARD_RECOVERYIMAGE_PARTITION_SIZE := 10485760
 BOARD_SYSTEMIMAGE_PARTITION_SIZE := 1157627904
 BOARD_USERDATAIMAGE_PARTITION_SIZE := 5930598400
+BOARD_CACHEIMAGE_FILE_SYSTEM_TYPE := ext4
+BOARD_CACHEIMAGE_PARTITION_SIZE := 560070656
 
 # Properties
 TARGET_SYSTEM_PROP += $(DEVICE_PATH)/system.prop