rxrpc: Fix a warning

Fix a warning due to an uninitialised variable.

le included from ../fs/afs/fs_probe.c:11:
../fs/afs/fs_probe.c: In function 'afs_fileserver_probe_result':
../fs/afs/internal.h:1453:2: warning: 'rtt_us' may be used uninitialized in this function [-Wmaybe-uninitialized]
 1453 |  printk("[%-6.6s] "FMT"\n", current->comm ,##__VA_ARGS__)
      |  ^~~~~~
../fs/afs/fs_probe.c:35:15: note: 'rtt_us' was declared here
Signed-off-by: David Howells <dhowells@redhat.com>

fs/afs/fs_probe.c

@@ -32,7 +32,7 @@ void afs_fileserver_probe_result(struct afs_call *call)
 	struct afs_server *server = call->server;
 	unsigned int server_index = call->server_index;
 	unsigned int index = call->addr_ix;
-	unsigned int rtt_us;
+	unsigned int rtt_us = 0;
 	bool have_result = false;
 	int ret = call->error;