sched/core: Remove unused prefetch_stack()

prefetch_stack() is defined by IA64, but not actually used anywhere anymore.

Remove it.

Acked-by: Linus Torvalds <[e-mail]>
Cc: Mike Galbraith <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>

arch/ia64/include/asm/processor.h

···
 #include <asm/ptrace.h>
 #include <asm/ustack.h>
 
-#define ARCH_HAS_PREFETCH_SWITCH_STACK
-
 #define IA64_NUM_PHYS_STACK_REG	96
 #define IA64_NUM_DBG_REGS	8
 

arch/ia64/kernel/entry.S

···
 	br.cond.sptk.many b7
 END(load_switch_stack)
 
-GLOBAL_ENTRY(prefetch_stack)
-	add r14 = -IA64_SWITCH_STACK_SIZE, sp
-	add r15 = IA64_TASK_THREAD_KSP_OFFSET, in0
-	;;
-	ld8 r16 = [r15]				// load next's stack pointer
-	lfetch.fault.excl [r14], 128
-	;;
-	lfetch.fault.excl [r14], 128
-	lfetch.fault [r16], 128
-	;;
-	lfetch.fault.excl [r14], 128
-	lfetch.fault [r16], 128
-	;;
-	lfetch.fault.excl [r14], 128
-	lfetch.fault [r16], 128
-	;;
-	lfetch.fault.excl [r14], 128
-	lfetch.fault [r16], 128
-	;;
-	lfetch.fault [r16], 128
-	br.ret.sptk.many rp
-END(prefetch_stack)
-
 	/*
 	 * Invoke a system call, but do some tracing before and after the call.
 	 * We MUST preserve the current register frame throughout this routine

include/linux/sched.h

···
 # define SCHED_FIXEDPOINT_SHIFT	10
 # define SCHED_FIXEDPOINT_SCALE	(1L << SCHED_FIXEDPOINT_SHIFT)
 
-#ifdef ARCH_HAS_PREFETCH_SWITCH_STACK
-extern void prefetch_stack(struct task_struct *t);
-#else
-static inline void prefetch_stack(struct task_struct *t) { }
-#endif
-
 struct load_weight {
 	unsigned long weight;
 	u32 inv_weight;