README: Use BOARD_VENDOR_SEPOLICY_DIRS

BOARD_SEPOLICY_DIRS is deprecated and references should be updated.

Signed-off-by: Felix <google@ix5.org>
Change-Id: I063940a63256a881206740e8a7ecae215f3a5ca8

README

@@ -18,21 +18,21 @@ newline inserted between each file as these are common failure
 points.
 
 These device policy files can be configured through the use of
-the BOARD_SEPOLICY_DIRS variable. This variable should be set
+the BOARD_VENDOR_SEPOLICY_DIRS variable. This variable should be set
 in the BoardConfig.mk file in the device or vendor directories.
 
-BOARD_SEPOLICY_DIRS contains a list of directories to search
+BOARD_VENDOR_SEPOLICY_DIRS contains a list of directories to search
 for additional policy files. Order matters in this list.
 For example, if you have 2 instances of widget.te files in the
-BOARD_SEPOLICY_DIRS search path, then the first one found (at the
+BOARD_VENDOR_SEPOLICY_DIRS search path, then the first one found (at the
 first search dir containing the file) will be concatenated first.
 Reviewing out/target/product/<device>/obj/ETC/sepolicy_intermediates/policy.conf
 will help sort out ordering issues.
 
 Example BoardConfig.mk Usage:
 From the Tuna device BoardConfig.mk, device/samsung/tuna/BoardConfig.mk
 
-BOARD_SEPOLICY_DIRS += device/samsung/tuna/sepolicy
+BOARD_VENDOR_SEPOLICY_DIRS += device/samsung/tuna/sepolicy
 
 Additionally, OEMs can specify BOARD_SEPOLICY_M4DEFS to pass arbitrary m4
 definitions during the build. A definition consists of a string in the form