ide: check rq->cmd_type in drive_cmd_intr()

drive_cmd_intr() is used by both REQ_TYPE_ATA_CMD and REQ_TYPE_ATA_TASK
but commands using PIO-in protocol are valid only for REQ_TYPE_ATA_CMD
(&args[4] in case of REQ_TYPE_ATA_TASK points to a value for IDE_LCYL_REG
register instead of the data buffer).  This fix allows REQ_TYPE_ATA_TASK
commands to use non-zero values for IDE_SECTOR_REG (args[3]).

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>