ata: libata-eh: Remove ata_do_eh()

ata: libata-eh: Remove ata_do_eh()

The only reason for ata_do_eh() to exist is that the two caller sites,
ata_std_error_handler() and ata_sff_error_handler() may pass it a
NULL hardreset operation so that the built-in (generic) hardreset
operation for a driver is ignored if the adapter SCR access is not
available.

However, ata_std_error_handler() and ata_sff_error_handler()
modifications of the hardreset port operation can easily be combined as
they are mutually exclusive. That is, a driver using sata_std_hardreset()
as its hardreset operation cannot use sata_sff_hardreset() and
vice-versa.

With this observation, ata_do_eh() can be removed and its code moved to
ata_std_error_handler(). The condition used to ignore the built-in
hardreset port operation is modified to be the one that was used in
ata_sff_error_handler(). This requires defining a stub for the function
sata_sff_hardreset() to avoid compilation errors when CONFIG_ATA_SFF is
not enabled. Furthermore, instead of modifying the local hardreset
operation definition, set the ATA_LFLAG_NO_HRST link flag to prevent
the use of built-in hardreset methods for ports without a valid scr_read
function. This flag is checked in ata_eh_reset() and if set, the
hardreset method is ignored.

This change simplifies ata_sff_error_handler() as this function now only
needs to call ata_std_error_handler().

No functional changes.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Niklas Cassel <cassel@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20250716020315.235457-2-dlemoal@kernel.org
Signed-off-by: Niklas Cassel <cassel@kernel.org>