Update SEPolicy flags for Android 12

* BOARD_PLAT_PUBLIC_SEPOLICY_DIR -> SYSTEM_EXT_PUBLIC_SEPOLICY_DIRS
* BOARD_PLAT_PRIVATE_SEPOLICY_DIR -> SYSTEM_EXT_PRIVATE_SEPOLICY_DIRS

Issue: FP3-A12#59
Change-Id: Ic0b029a0678004fbe3d8e311723ecf00eeef08ac
1 file changed