Account for multiple BOARD_PLAT_PUBLIC[PRIVATE]_SEPOLICY_DIR dirs

After https://android-review.googlesource.com/688488
BOARD_PLAT_PUBLIC[PRIVATE]_SEPOLICY_DIR can now specify multiple
directories.

Bug: n/a
Test: build sepolicy
Change-Id: I838c76736a3f1bd8759e24739cf82fea33a531b4
diff --git a/android/config.go b/android/config.go
index 7f2a3ac..bc3d4f5 100644
--- a/android/config.go
+++ b/android/config.go
@@ -811,12 +811,12 @@
 	return c.config.productVariables.BoardOdmSepolicyDirs
 }
 
-func (c *deviceConfig) PlatPublicSepolicyDir() string {
-	return c.config.productVariables.BoardPlatPublicSepolicyDir
+func (c *deviceConfig) PlatPublicSepolicyDirs() []string {
+	return c.config.productVariables.BoardPlatPublicSepolicyDirs
 }
 
-func (c *deviceConfig) PlatPrivateSepolicyDir() string {
-	return c.config.productVariables.BoardPlatPrivateSepolicyDir
+func (c *deviceConfig) PlatPrivateSepolicyDirs() []string {
+	return c.config.productVariables.BoardPlatPrivateSepolicyDirs
 }
 
 func (c *config) IntegerOverflowDisabledForPath(path string) bool {