Staging: lustre: lnet: selftest: Made a function static.

The following patch makes a function static as it is not used by other
files.
The patch fixes the warning:
WARNING: symbol 'brw_server_rpc_done' was not declared. Should it be static?

The above warning was reported by sparse.
Signed-off-by: Heena Sirwani <heenasirwani@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lnet/selftest/brw_test.c

@@ -358,7 +358,7 @@ brw_client_done_rpc(sfw_test_unit_t *tsu, srpc_client_rpc_t *rpc)
 	return;
 }
 
-void
+static void
 brw_server_rpc_done(srpc_server_rpc_t *rpc)
 {
 	srpc_bulk_t *blk = rpc->srpc_bulk;