ahci: don't enable port irq before handler is registered

ahci: don't enable port irq before handler is registered

The ahci_pmp_attach() & ahci_pmp_detach() unmask port irqs, but they
are also called during port initialization, before ahci host irq
handler is registered. On ce4100 platform, this sometimes triggers
"irq 4: nobody cared" message when loading driver.

Fixed this by not touching the register if the port is in frozen
state, and mark all uninitialized port as frozen.

Signed-off-by: Maxime Bizon <[email protected]>
Acked-by: Tejun Heo <[email protected]>
Cc: [email protected]
Signed-off-by: Jeff Garzik <[email protected]>