libata-acpi: improve ACPI disabling
* If _GTF evalution fails, it's pointless to retry. If nothing else
is wrong, just ignore the error.
* After disabling ACPI, return success iff the number of executed _GTF
command equals zero. Otherwise, tell EH to retry. This change
fixes bogus 1 return bug where ata_acpi_on_devcfg() expects the
caller to reload IDENTIFY data and continue but the caller
interprets it as an error.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>