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 <[e-mail]>

net/sunrpc/backchannel_rqst.c

···
 	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.
···
 	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

net/sunrpc/svc.c

···
 		return 0;
 	}
 }
-EXPORT_SYMBOL(bc_svc_process);
+EXPORT_SYMBOL_GPL(bc_svc_process);
 #endif /* CONFIG_SUNRPC_BACKCHANNEL */
 
 /*

net/sunrpc/xdr.c

···
 	kaddr[buf->page_base + len] = '\0';
 	kunmap_atomic(kaddr, KM_USER0);
 }
-EXPORT_SYMBOL(xdr_terminate_string);
+EXPORT_SYMBOL_GPL(xdr_terminate_string);
 
 void
 xdr_encode_pages(struct xdr_buf *xdr, struct page **pages, unsigned int base,