ata: libata: Rename ATA_DFLAG_NCQ_PRIO_ENABLE

Rename ATA_DFLAG_NCQ_PRIO_ENABLE to ATA_DFLAG_NCQ_PRIO_ENABLED to match
the fact that this flags indicates if NCQ priority use is enabled by the
user.

Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>