btrfs: sink parameter len to alloc_extent_buffer

Because we're using globally known nodesize. Do the same for the sanity
test function variant.

Signed-off-by: David Sterba <dsterba@suse.cz>
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index e6553e3..71268e5 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -262,7 +262,7 @@
 void set_page_extent_mapped(struct page *page);
 
 struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info,
-					  u64 start, unsigned long len);
+					  u64 start);
 struct extent_buffer *alloc_dummy_extent_buffer(struct btrfs_fs_info *fs_info,
 		u64 start);
 struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src);
@@ -378,5 +378,5 @@
 				      u64 *end, u64 max_bytes);
 #endif
 struct extent_buffer *alloc_test_extent_buffer(struct btrfs_fs_info *fs_info,
-					       u64 start, unsigned long len);
+					       u64 start);
 #endif