fix yaffs build failure on 2.6.28.2 (thanks to Alexandros C. Couloumbis <alex@ozo.com>)

SVN-Revision: 14250

target/linux/generic-2.6/patches-2.6.28/512-yaffs-2.6.28.1-fix.patch

+--- a/fs/yaffs2/yaffs_fs.c
++++ b/fs/yaffs2/yaffs_fs.c
+@@ -745,7 +745,7 @@ static int yaffs_write_begin(struct file
+         
+ 	T(YAFFS_TRACE_OS, (KERN_DEBUG "start yaffs_write_begin\n"));
+ 	/* Get a page */
+-	pg = __grab_cache_page(mapping,index);
++	pg = grab_cache_page_write_begin(mapping, index, flags);
+ 	*pagep = pg;	
+ 	if(!pg){
+ 		ret =  -ENOMEM;