Add selinux permissions for ro.usb.uvc.enabled

This CL the selinux rules for the property ro.usb.uvc.enabled which will
be used to toggle UVC Gadget functionality on the Android Device.

Bug: 242344221
Bug: 242344229
Test: Manually tested that the property can only be read at runtime,
      not written to.
Change-Id: I0fd6051666d9554037acc68fa81226503f514a45
diff --git a/private/property_contexts b/private/property_contexts
index 5611290..f3c8d55 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -1501,3 +1501,6 @@
 
 # Adaptive haptics settings property
 vibrator.adaptive_haptics.enabled u:object_r:adaptive_haptics_prop:s0 exact string
+
+# UVC Gadget property
+ro.usb.uvc.enabled      u:object_r:usb_uvc_enabled_prop:s0 exact bool