x86: uv: Use irq_alloc/free_hwirq()

x86: uv: Use irq_alloc/free_hwirq()

No functional change. The request to allocate the irq above
NR_IRQS_LEGACY is completely pointless as the implementation enforces
that the dynamic allocations are above the GSI interrupts, which
includes the legacy PIT irqs.

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>
Cc: x86@kernel.org
Link: http://lkml.kernel.org/r/20140507154335.252789823@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>