ARC: add TLS support for ARCv3

For ARCv3 the register is fixed to r30, so we don't need to
configure it at compile-time.

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