x86: htirq: Use irq_alloc/free_irq()

No functional change, just cleaned up a bit.

This does not replace the requirement to move x86 to irq domains, but
it limits the mess to some degree.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Grant Likely <grant.likely@linaro.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: x86@kernel.org
Cc: linux-pci@vger.kernel.org
Link: http://lkml.kernel.org/r/20140507154335.452206351@linutronix.de


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>