ARC: doc: update ARC HW & tools support status

List of the changes:
 * update info about ARCv3 HS6x which support has been upstreamed
   recently
 * mark HS3x userspace support as Y

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