SUNRPC: Convert the backchannel exports to EXPORT_SYMBOL_GPL

Ensure that the backchannel exports conform to the existing sunrpc
practice.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/net/sunrpc/backchannel_rqst.c b/net/sunrpc/backchannel_rqst.c
index bb5593f..91eaa26 100644
--- a/net/sunrpc/backchannel_rqst.c
+++ b/net/sunrpc/backchannel_rqst.c
@@ -172,7 +172,7 @@
 	dprintk("RPC:       setup backchannel transport failed\n");
 	return -1;
 }
-EXPORT_SYMBOL(xprt_setup_backchannel);
+EXPORT_SYMBOL_GPL(xprt_setup_backchannel);
 
 /*
  * Destroys the backchannel preallocated structures.
@@ -202,7 +202,7 @@
 	dprintk("RPC:        backchannel list empty= %s\n",
 		list_empty(&xprt->bc_pa_list) ? "true" : "false");
 }
-EXPORT_SYMBOL(xprt_destroy_backchannel);
+EXPORT_SYMBOL_GPL(xprt_destroy_backchannel);
 
 /*
  * One or more rpc_rqst structure have been preallocated during the