sepolicy(nfc): Changing selinux policy for signed NFC APK

NFC stack is becoming an unbundled apex which embeds the existing NFC
APK. Unbundling requires the apex & apk to be signed by non-platform
certificates, hence adding new seapp_contexts rule for the NFC stack.

The old rule is also left behing to support `-next` config builds where
we are still using the platform signed NFC APK.

Ignore-AOSP-First: All of the NFC mainline work is only present in
internal master. Will cherry-pick this CL once we cherry-pick all its
dependencies.

Bug: 320583956
Test: Bootup test with signed NFC APK (within NFC apex)
Change-Id: I1d4d6370cce558c8dcc0ec73a7ce47c2b5495a33
diff --git a/private/mac_permissions.xml b/private/mac_permissions.xml
index c9a9aca..fa8ffcf 100644
--- a/private/mac_permissions.xml
+++ b/private/mac_permissions.xml
@@ -69,4 +69,9 @@
     <signer signature="@NETWORK_STACK" >
       <seinfo value="network_stack" />
     </signer>
+
+    <!-- NFC key in AOSP -->
+    <signer signature="@NFC" >
+      <seinfo value="nfc" />
+    </signer>
 </policy>