ia64/tlb: Eradicate tlb_migrate_finish() callback

Only ia64-sn2 uses this as an optimization, and there it is of
questionable correctness due to the mm_users==1 test.

Remove it entirely.

No change in behavior intended.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/asm-generic/tlb.h

@@ -604,8 +604,4 @@ static inline void tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vm
 
 #endif /* CONFIG_MMU */
 
-#ifndef tlb_migrate_finish
-#define tlb_migrate_finish(mm) do {} while (0)
-#endif
-
 #endif /* _ASM_GENERIC__TLB_H */