aoe: WIN_* -> ATA_CMD_*

* Use ATA_CMD_* defines instead of WIN_* ones.

* Include <linux/ata.h> directly instead of through <linux/hdreg.h>.

Cc: Ed L. Cashin <ecashin@coraid.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>