Adding labeling for vendor security patch prop

This will allow adb shell getprop ro.vendor.build.security_patch to
properly return the correct build property, whereas previously it was
offlimits due to lack of label.

Test: adb shell getprop ro.vendor.build.security_patch successfully
returns whatever VENDOR_SECURITY_PATCH is defined to be in the Android
.mk files

Change-Id: Ie8427738125fc7f909ad8d51e4b76558f5544d49
diff --git a/private/compat/27.0/27.0.ignore.cil b/private/compat/27.0/27.0.ignore.cil
index a3f7bb5..5428d83 100644
--- a/private/compat/27.0/27.0.ignore.cil
+++ b/private/compat/27.0/27.0.ignore.cil
@@ -91,6 +91,7 @@
     usbd_tmpfs
     vendor_default_prop
     vendor_init
+    vendor_security_patch_level_prop
     vendor_shell
     vold_metadata_file
     vold_prepare_subdirs