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>
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 57ab7e4..5647055 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -734,7 +734,7 @@
 			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);