Create root folders outside of vendor init script

 * The core SELinux policies for vendor_init are being restricted as to
   comply with Treble. Simply adding a local rule to allow creating
   folders under rootfs would be enough, but at the same time defining
   the extra root folders and making use of AID/fs configuration file
   to set perms is more neat and clean. This seems not to be required
   when the partitions are mounted directly under rootfs, however it's
   not the case here because radio and adsp partitions are respectively
   mounted under /firmware/radio and /firmware/adsp and therefore
   /firmware must exist beforehand. While at it, drop the creation
   of persist root folder as there's no evidence of HTC MSM8974-based
   devices even having such partition.

Change-Id: Idabd7ae72e4c4fd9daac5ba3be3e6236f79f251b
diff --git a/BoardConfig.mk b/BoardConfig.mk
index 732ef56..8326ccc 100644
--- a/BoardConfig.mk
+++ b/BoardConfig.mk
@@ -84,6 +84,7 @@
 BOARD_PERSISTIMAGE_FILE_SYSTEM_TYPE := ext4
 BOARD_PERSISTIMAGE_PARTITION_SIZE := 5242880
 BOARD_RECOVERYIMAGE_PARTITION_SIZE := 0x01000000
+BOARD_ROOT_EXTRA_FOLDERS := firmware persist
 BOARD_SYSTEMIMAGE_PARTITION_SIZE := 2147483648
 BOARD_TOMBSTONESIMAGE_PARTITION_SIZE := 73400320
 BOARD_USERDATAIMAGE_PARTITION_SIZE := 27358941675