The DIAGNOSE command in the qemu IDE implementation has an error when
use dfor packet devices.
The status register value is dependant on the drive being a packet
device or not, this patch corrects the returned status.
From the ATA/PI specification (V6 draft):
"If the device implements the PACKET command feature set, the device
SHALL clear bits 6,5,4,3,2 and 0 in the Status register to zero."
A selection of physical devices have been checked and do conform to
the specifications behaviour.
Signed-off-by: Vincent Sanders <address@hidden>