m68knommu: use MCF_IRQ_PIT1 instead of MCFINT_VECBASE + MCFINT_PIT1

use MCF_IRQ_PIT1 instead of MCFINT_VECBASE + MCFINT_PIT1 so we can support
those parts that have the pit1 interrupt on other than the first interrupt
controller.

Signed-off-by: Steven King <sfking@fdwdc.com>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>