nios2: TLB handling

This patch adds the TLB maintenance functions.

Signed-off-by: Ley Foon Tan <lftan@altera.com>

diff --cc arch/nios2/include/asm/tlb.h
Simple merge

diff --cc arch/nios2/include/asm/tlbflush.h
Simple merge

diff --cc arch/nios2/mm/tlb.c
Simple merge