builtin/fetch.c: Fix a sparse warning

Sparse issues an "'prepare_transport' was not declared. Should it
be static?" warning. In order to suppress the warning, since this
symbol only requires file scope, we simply add the static modifier
to it's declaration.

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fetch.c

@@ -734,7 +734,7 @@ static void set_option(struct transport *transport, const char *name, const char
 			name, transport->url);
 }
 
-struct transport *prepare_transport(struct remote *remote)
+static struct transport *prepare_transport(struct remote *remote)
 {
 	struct transport *transport;
 	transport = transport_get(remote, NULL);