Add FDT support for dwiic(4)

Introduce iic_intr_disestablish() and use it in ihidev(4).

ok jcs@

Cleanup <sys/kthread.h> and <sys/proc.h> includes.

Do not include <sys/kthread.h> where it is not needed and stop including
<sys/proc.h> in it.

ok visa@, anton@

fetch timing parameters from ACPI like the ACPI attachment does
since those fetched from the controller may not be correct

also attach on intel 300 series devices

ok kettenis

dwiic: cleanup function prototypes after ACPI/PCI split

Add PCI attachment for dwiic(4) needed by Intel 100 Series machines

ok kettenis