[PATCH] powerpc: iSeries fixes for build with no PCI

This reverts part of "ppc64 iSeries: allow build with no PCI"
(145d01e4287b8cbf50f87c3283e33bf5c84e8468) which affected generic code
and applies a fix in the arch specific code.

Commit "partly merge iseries do_IRQ"
(5fee9b3b39eb55c7e3619a3b36ceeabffeb8f144) introduced iSeries_get_irq
which was only available if CONFIG_PCI is set.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>