powerpc/mpic: Fix problem that affinity is not updated

powerpc/mpic: Fix problem that affinity is not updated

commit 38e1313fc753482b93aa6c6f11cfbd43a5bcd963 upstream.

Since commit 57b150cce8e004ddd36330490a68bfb59b7271e9, desc->affinity
of an irq is changed after calling desc->chip->set_affinity.
Therefore we need to fix the irq_choose_cpu() not to depend on the
desc->affinity for new mask.

Signed-off-by: Jiajun Wu <b06378@freescale.com>
Signed-off-by: Li Yang <leoli@freescale.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>