ARC: Basic refactoring of registers layer

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
ARC: Working implementation but very dirty

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
ARC: Works with every test

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>
Reorganize enum for registers

Still a bit inconsistent and missing optional registers...

Signed-off-by: Anton Kolesov <anton.kolesov@synopsys.com>