udf: Add handling of in-ICB files to udf_bmap()

Add detection of in-ICB files to udf_bmap() and return error in that
case. This will allow us o use single address_space_operations in UDF.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>