Separate the fstab file between grouper and tilapia

Because tilapia has the radio image partition which recovery
knows how to update, we can no longer have a unified fstab
for the two products.

Change-Id: I8c45d4e813e1e0a7379524ba4d7465d2d6568641
diff --git a/BoardConfig.mk b/BoardConfig.mk
index 0e3258e..f5f9227 100644
--- a/BoardConfig.mk
+++ b/BoardConfig.mk
@@ -40,6 +40,8 @@
 -include vendor/asus/grouper/BoardConfigVendor.mk
 include device/asus/grouper/BoardConfigCommon.mk
 
+TARGET_RECOVERY_FSTAB = device/asus/grouper/fstab.grouper
+
 BOARD_SEPOLICY_DIRS := \
         device/asus/grouper/sepolicy