x86/irq: remove offline CPUs from old CPU mask when adjusting move_cleanup_count

x86/irq: remove offline CPUs from old CPU mask when adjusting move_cleanup_count

When adjusting move_cleanup_count to account for CPUs that are offline also
adjust old_cpu_mask, otherwise further calls to fixup_irqs() could subtract
those again and create an imbalance in move_cleanup_count.

Fixes: 472e0b74c5c4 ('x86/IRQ: deal with move cleanup count state in fixup_irqs()')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>