Add BoardPlatVendorPolicy to soong config

Bug: 205924657
Test: build
Change-Id: Ia0fe4fd916e539ee04aa0e8343068cc03bd9787c
diff --git a/android/variable.go b/android/variable.go
index 158d264..a7068108 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -347,6 +347,7 @@
 	BoardVendorSepolicyDirs      []string `json:",omitempty"`
 	BoardOdmSepolicyDirs         []string `json:",omitempty"`
 	BoardReqdMaskPolicy          []string `json:",omitempty"`
+	BoardPlatVendorPolicy        []string `json:",omitempty"`
 	SystemExtPublicSepolicyDirs  []string `json:",omitempty"`
 	SystemExtPrivateSepolicyDirs []string `json:",omitempty"`
 	BoardSepolicyM4Defs          []string `json:",omitempty"`