Btrfs: remove BUG() in btrfs_extent_inline_ref_size

Now that btrfs_get_extent_inline_ref_type() can report if type is a
valid one and all callers can gracefully deal with that, we don't need
to crash here.
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -1804,7 +1804,6 @@ static inline u32 btrfs_extent_inline_ref_size(int type)
 	if (type == BTRFS_EXTENT_DATA_REF_KEY)
 		return sizeof(struct btrfs_extent_data_ref) +
 		       offsetof(struct btrfs_extent_inline_ref, offset);
-	BUG();
 	return 0;
 }