sched: clean up include files in sched.c

#include <linux/module.h>

#include <linux/nmi.h>

#include <linux/init.h>

#include <asm/uaccess.h>

#include <linux/uaccess.h>

#include <linux/highmem.h>

#include <linux/smp_lock.h>

#include <asm/mmu_context.h>

#include <linux/kprobes.h>

#include <linux/delayacct.h>

#include <linux/reciprocal_div.h>

#include <linux/unistd.h>

#include <asm/tlb.h>

#include <asm/unistd.h>

/*

 * Scheduler clock - returns current time in nanosec units.