nios2: Library functions

Add optimised library functions for nios2.

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

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

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

diff --cc arch/nios2/lib/memcpy.c
Simple merge

diff --cc arch/nios2/lib/memmove.c
Simple merge

diff --cc arch/nios2/lib/memset.c
Simple merge