Fold iblock_emulate_read_cap_with_block_size() into its only caller.

Link: https://lore.kernel.org/r/20220927082225.271975-1-hch@lst.deReviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>