Convert AHCI to new EH. Unfortunately, ICH7 AHCI reacts badly if IRQ mask is diddled during operation. So, freezing is implemented by unconditionally clearing interrupt conditions while frozen. * Interrupts are categorized according to required action. e.g. Connection status or unknown FIS error requires freezing the port while TF or HBUS_DATA don't. * Only CONNECT (reflects SErr.X) interrupt is taken into account not PHYRDY (SErr.N), as CONNECT is better cue for starting EH. * AHCI may be invoked without any active command. e.g. CONNECT irq occuring while no qc in progress still triggers EH and will reset the port and revalidate attached device. Signed-off-by: Tejun Heo <htejun@gmail.com>