Use PRODUCT_*_SEPOLICY_DIRS to build product sepolicy.

This places to product-specific sepolicy on /product. This CL is like
I67636b7aaff2bd5ae5309981f9fa2f8ce51edf6f in aosp, but for bonito.

Bug: 119305624
Test: m selinux_policy
Change-Id: I0fd59970132b33cd0a0fabaac003b3d1b697e25b

diff --git a/bonito-sepolicy.mk b/bonito-sepolicy.mk
index 82a1465..6ac0dea 100644
--- a/bonito-sepolicy.mk
+++ b/bonito-sepolicy.mk

@@ -1,5 +1,5 @@
-BOARD_PLAT_PUBLIC_SEPOLICY_DIR := device/google/bonito-sepolicy/public
-BOARD_PLAT_PRIVATE_SEPOLICY_DIR := device/google/bonito-sepolicy/private
+PRODUCT_PUBLIC_SEPOLICY_DIRS := device/google/bonito-sepolicy/public
+PRODUCT_PRIVATE_SEPOLICY_DIRS := device/google/bonito-sepolicy/private
 
 # vendors
 BOARD_SEPOLICY_DIRS += device/google/bonito-sepolicy/vendor/qcom/common