This adds support for the MPC52xx Interrupt controller for
ARCH=powerpc.

It includes the main code in arch/powerpc/sysdev/ as well as a header
file in include/asm-powerpc.
Signed-off-by: Nicolas DET <nd@bplan-gmbh.de>
Acked-by: Sylvain Munaut <tnt@246tNt.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Paul Mackerras <paulus@samba.org>