ata: libata: Remove ATA_DFLAG_ZAC device flag

The ATA device flag ATA_DFLAG_ZAC is used to indicate if a devie is a
host managed or host aware zoned device. However, this flag is not used
in the hot path and only used during device scanning/revalidation and
for inquiry and sense SCSI command translation.

Save one bit from struct ata_device flags field by replacing this flag
with the internal helper function ata_dev_is_zac(). This function
returns true if the device class is ATA_DEV_ZAC (host managed ZAC device
case) or if its identify data reports it supports the zoned command set
(host aware ZAC device case).

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Niklas Cassel <cassel@kernel.org>