ata: libata: remove references to non-existing error_handler()

With commit 65a15d65 ("scsi: ipr: Remove SATA support") all
libata drivers now have the error_handler() callback provided,
so we can stop checking for non-existing error_handler callback.

Signed-off-by: Hannes Reinecke <hare@suse.de>
[niklas: fixed review comments, rebased, solved conflicts during rebase,
fixed bug that unconditionally dumped all QCs, removed the now unused
function ata_dump_status(), removed the now unreachable failure paths in
atapi_qc_complete(), removed the non-EH function to request ATAPI sense]
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>