system_queries: Add netlink based delete

We shouldn't depend on calling the IP binary

Change-Id: I4e9b3229ef936dad96e2fcfcea8f6b32a9c9f801
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/src/system_queries.hpp b/src/system_queries.hpp
index 4c187c7..9027cb3 100644
--- a/src/system_queries.hpp
+++ b/src/system_queries.hpp
@@ -18,4 +18,6 @@
 
 void setNICUp(std::string_view ifname, bool up);
 
+void deleteIntf(unsigned idx);
+
 } // namespace phosphor::network::system