x86/ioapic: Simplify ioapic_setup_resources()

Optimize the function by removing the variable 'num'.

Signed-off-by: Rui Wang <rui.y.wang@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: tony.luck@intel.com
Cc: linux-pci@vger.kernel.org
Cc: rjw@rjwysocki.net
Cc: linux-acpi@vger.kernel.org
Cc: bhelgaas@google.com
Link: http://lkml.kernel.org/r/1465369193-4816-4-git-send-email-rui.y.wang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>