x86, io_apic: remove duplicated include from irq_remapping.c

Remove duplicated include.
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Joerg Roedel <joro@8bytes.org>

drivers/iommu/irq_remapping.c

@@ -2,7 +2,6 @@
 #include <linux/cpumask.h>
 #include <linux/kernel.h>
 #include <linux/string.h>
-#include <linux/cpumask.h>
 #include <linux/errno.h>
 #include <linux/msi.h>
 #include <linux/irq.h>