page-server: Make open_page_server_xfer static

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/page-xfer.h

@@ -26,7 +26,6 @@ struct page_xfer {
 };
 
 int open_page_xfer(struct page_xfer *xfer, int fd_type, long id);
-int open_page_server_xfer(struct page_xfer *, int fd_type, long id);
 struct page_pipe;
 int page_xfer_dump_pages(struct page_xfer *, struct page_pipe *,
 		unsigned long off);

page-xfer.c

@@ -250,7 +250,7 @@ static void close_server_xfer(struct page_xfer *xfer)
 	xfer->fd = -1;
 }
 
-int open_page_server_xfer(struct page_xfer *xfer, int fd_type, long id)
+static int open_page_server_xfer(struct page_xfer *xfer, int fd_type, long id)
 {
 	xfer->fd = page_server_sk;
 	xfer->write_pagemap = write_pagemap_to_server;