btrfs: make extent_range_redirty_for_io return void

Does not return any errors, nor anything from the callgraph. There's a
BUG_ON but it's a sanity check and not an error condition we could
recover from.

Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index e55a728..f06800e 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -1466,7 +1466,7 @@
 	}
 }
 
-int extent_range_redirty_for_io(struct inode *inode, u64 start, u64 end)
+void extent_range_redirty_for_io(struct inode *inode, u64 start, u64 end)
 {
 	unsigned long index = start >> PAGE_CACHE_SHIFT;
 	unsigned long end_index = end >> PAGE_CACHE_SHIFT;
@@ -1480,7 +1480,6 @@
 		page_cache_release(page);
 		index++;
 	}
-	return 0;
 }
 
 /*