irq_remapping: Remove unused header files

seq_file.h does not need to be included,so remove it.
Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/irq_remapping.c

-#include <linux/seq_file.h>
 #include <linux/cpumask.h>
 #include <linux/kernel.h>
 #include <linux/string.h>