nios2: rework cache

- flush dcache before flush instruction cache
- remork update_mmu_cache and flush_dcache_page
- add shmparam.h

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

diff --cc arch/nios2/include/asm/Kbuild
Simple merge

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

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