udmabuf: use pgoff_t for pagecount

Reported-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20180911134216.9760-4-kraxel@redhat.com

drivers/dma-buf/udmabuf.c

@@ -13,7 +13,7 @@
 #include <linux/udmabuf.h>
 
 struct udmabuf {
-	u32 pagecount;
+	pgoff_t pagecount;
 	struct page **pages;
 };