hw/ide/ahci: PxCI should not get cleared when ERR_STAT is set

hw/ide/ahci: PxCI should not get cleared when ERR_STAT is set

For NCQ, PxCI is cleared on command queued successfully.
For non-NCQ, PxCI is cleared on command completed successfully.
Successfully means ERR_STAT, BUSY and DRQ are all cleared.

A command that has ERR_STAT set, does not get to clear PxCI.
See AHCI 1.3.1, section 5.3.8, states RegFIS:Entry and RegFIS:ClearCI,
and 5.3.16.5 ERR:FatalTaskfile.

In the case of non-NCQ commands, not clearing PxCI is needed in order
for host software to be able to see which command slot that failed.

Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Message-id: 20230609140844.202795-7-nks@flawful.org
Signed-off-by: John Snow <jsnow@redhat.com>