hv: rename prep_negotiate_resp() to vmbus_prep_negotiate_resp()

It's a global symbol, so properly prefix it and use the proper EXPORT
value as well.

Cc: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 4c8414a..98a57a5 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -960,7 +960,7 @@
 	void (*callback) (void *context);
 };
 
-extern void prep_negotiate_resp(struct icmsg_hdr *,
-				struct icmsg_negotiate *, u8 *);
+extern void vmbus_prep_negotiate_resp(struct icmsg_hdr *,
+				      struct icmsg_negotiate *, u8 *);
 
 #endif /* _HYPERV_H */