btrfs: Use locked_end rather than open coding it

Right before we go into this loop locked_end is set to alloc_end - 1 and
is being used in nearby functions, no need to have exceptions. This just
makes the code consistent, no functional changes.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 89fb9ef..559d716 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2896,8 +2896,8 @@
 		 */
 		lock_extent_bits(&BTRFS_I(inode)->io_tree, alloc_start,
 				 locked_end, &cached_state);
-		ordered = btrfs_lookup_first_ordered_extent(inode,
-							    alloc_end - 1);
+		ordered = btrfs_lookup_first_ordered_extent(inode, locked_end);
+
 		if (ordered &&
 		    ordered->file_offset + ordered->len > alloc_start &&
 		    ordered->file_offset < alloc_end) {