[PATCH] powerpc: Move xics.[ch] into platforms/pseries

This patch moves the XICS interrupt controller code into the
platforms/pseries directory, since it only appears on pSeries
machines.  If it ever appears on some other machine we can move it to
sysdev, although xics.c itself will need a bunch of changes in that
case to remove pSeries specific assumptions.

Signed-off-by: David Gibson <dwg@au1.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>