Allow NFC to read/write nfc. system properties.

(cherry pick of commit 05383ebfb439bed8436912ed28db550e8842b343)

Bug: 17298769
Change-Id: I1994ff9f9da9b13249099f6c9bcec88dcdc2bb97
diff --git a/property_contexts b/property_contexts
index 48f7fae..f89c432 100644
--- a/property_contexts
+++ b/property_contexts
@@ -58,3 +58,6 @@
 ctl.bugreport           u:object_r:ctl_bugreport_prop:s0
 ctl.dhcpcd_bt-pan       u:object_r:ctl_dhcp_pan_prop:s0
 ctl.                    u:object_r:ctl_default_prop:s0
+
+# NFC properties
+nfc.                    u:object_r:nfc_prop:s0