[SPARC64] mm: Do not flush TLB mm in tlb_finish_mmu()

It isn't needed any longer, as noted by Hugh Dickins.

We still need the flush routines, due to the one remaining
call site in hugetlb_prefault_arch_hook().  That can be
eliminated at some later point, however.

Signed-off-by: David S. Miller <davem@davemloft.net>