display: Avoid selinux denials for vendor.debug.egl.swapinterval

Graphics prebuilts from gfx promotion #0062.03 introduce additional property acccess
 vendor.debug.egl.swapinterval
Add sepolicy to let bootanimation/apps access it cleanly.
This is a regression issue from ag/4888277 which leads to log flooding of access denials.

Bug: 117629985
Test: device logs does not throw following error:
      E libc    : Access denied finding property "vendor.debug.egl.swapinterval"
Change-Id: I28f13e60c679ab041abed65d848f492c5c9a9ce6
(cherry picked from commit cccfdee4ad0b2ea0f40beb2ebc2a0193d77fc8cb)
diff --git a/sepolicy/vendor/property_contexts b/sepolicy/vendor/property_contexts
index 112fcfa..773a4c3 100644
--- a/sepolicy/vendor/property_contexts
+++ b/sepolicy/vendor/property_contexts
@@ -50,6 +50,7 @@
 vendor.debug.egl.changepixelformat  u:object_r:public_vendor_default_prop:s0
 vendor.debug.prerotation.disable  u:object_r:public_vendor_default_prop:s0
 vendor.debug.rs.           u:object_r:public_vendor_default_prop:s0
+vendor.debug.egl.swapinterval      u:object_r:public_vendor_default_prop:s0
 
 # public_vendor_system_prop
 # They are public_vendor_system_props for vendor-specific extension.