[POWERPC] Update mpc7448hpc2 board irq support using device tree

The patch rewrites mpc7448hpc2 board irq support according to the new
mpic device tree interface.

Signed-off-by: Roy Zang	<tie-fei.zang@freescale.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
5 files changed