android/: Rename Plat->SystemExt*SepolicyDirs

Align with changes in system/sepolicy and build/make.

Signed-off-by: Felix <google@ix5.org>
Change-Id: I326962648a78e68e8cc83fdc22d8274eaecb8c8c
diff --git a/android/variable.go b/android/variable.go
index 3c08405..591e2a9 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -302,8 +302,8 @@
 
 	BoardVendorSepolicyDirs      []string `json:",omitempty"`
 	BoardOdmSepolicyDirs         []string `json:",omitempty"`
-	BoardPlatPublicSepolicyDirs  []string `json:",omitempty"`
-	BoardPlatPrivateSepolicyDirs []string `json:",omitempty"`
+	SystemExtPublicSepolicyDirs  []string `json:",omitempty"`
+	SystemExtPrivateSepolicyDirs []string `json:",omitempty"`
 	BoardSepolicyM4Defs          []string `json:",omitempty"`
 
 	BoardVndkRuntimeDisable *bool `json:",omitempty"`