x86, irq: Remove pointless irq_reserve_irqs() call

That's a leftover from the time where x86 supported SPARSE_IRQ=n.

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>
Cc: x86@kernel.org
Link: http://lkml.kernel.org/r/20140507154338.967285614@linutronix.de


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