Support TCP based fastbootd in recovery mode.

The IPv6 link-local address is used to avoid expose device to out of
network segment.

BUG: 155198345
Test: manual test.
Change-Id: I0ce8c12de9976c01e57a6433c7fb50235e907dc5
diff --git a/private/property_contexts b/private/property_contexts
index cfcfd5e..c4eb3aa 100644
--- a/private/property_contexts
+++ b/private/property_contexts
@@ -94,6 +94,9 @@
 sys.lmk.                u:object_r:system_lmk_prop:s0
 sys.trace.              u:object_r:system_trace_prop:s0
 
+# Fastbootd protocol control property
+fastbootd.protocol    u:object_r:fastbootd_protocol_prop:s0 exact enum usb tcp
+
 # Boolean property set by system server upon boot indicating
 # if device is fully owned by organization instead of being
 # a personal device.