btrfs: make extent_range_clear_dirty_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 0ea3e99..e55a728 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -1451,7 +1451,7 @@
 				GFP_NOFS);
 }
 
-int extent_range_clear_dirty_for_io(struct inode *inode, u64 start, u64 end)
+void extent_range_clear_dirty_for_io(struct inode *inode, u64 start, u64 end)
 {
 	unsigned long index = start >> PAGE_CACHE_SHIFT;
 	unsigned long end_index = end >> PAGE_CACHE_SHIFT;
@@ -1464,7 +1464,6 @@
 		page_cache_release(page);
 		index++;
 	}
-	return 0;
 }
 
 int extent_range_redirty_for_io(struct inode *inode, u64 start, u64 end)