sepolicy: Add permission for formatting user/cache partition

If the "formattable" fstab flag is set, init will tries
to format that partition, added the required policy to allow it.

Change-Id: I858b06aa3ff3ce775cf7676b09b9960f2558f7f6
diff --git a/sepolicy/init.te b/sepolicy/init.te
new file mode 100644
index 0000000..447c720
--- /dev/null
+++ b/sepolicy/init.te
@@ -0,0 +1,4 @@
+# Allow formatting userdata or cache partitions
+allow init block_device:dir search;
+allow init userdata_block_device:blk_file rw_file_perms;
+allow init cache_block_device:blk_file rw_file_perms;