nios2: Page table management

This patch adds support for page table management.

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

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

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

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

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