__assign_irq_vector() uses the vector_cpumask which is assigned by
apic->vector_allocation_domain() without doing basic sanity checks. That can
result in a situation where the final assignement of a newly found vector
fails in apic->cpu_mask_to_apicid_and(). So we have to do rollbacks for no
reason.

apic->cpu_mask_to_apicid_and() only fails if 

  vector_cpumask & requested_cpumask & cpu_online_mask 

is empty.

Check for this condition right away and if the result is empty try immediately
the next possible cpu in the requested mask. So in case of a failure the old
setting is unchanged and we can remove the rollback code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Borislav Petkov <bp@alien8.de>
Tested-by: Joe Lawrence <joe.lawrence@stratus.com>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Jeremiah Mahler <jmmahler@gmail.com>
Cc: andy.shevchenko@gmail.com
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: stable@vger.kernel.org #4.3+
Link: http://lkml.kernel.org/r/20151231160106.561877324@linutronix.deSigned-off-by: Thomas Gleixner <tglx@linutronix.de>