ARC: split sys-io for common and ARCv2-only parts

Split ARC sys-io.h implementation for two part:
 * AUX reg accessors - ASM based which and valid for ARCv2
 * MMIO accessors - writen in C and valid for both ARCv2 and ARCv3

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Evgeniy Paltsev <PaltsevEvgeniy@gmail.com>
3 files changed