MAINTAINERS: migrate arc timer driver from CODEOWNERS

Migrate drivers/timer/*arcv2* from CODEOWNERS to MAINTAINERS
by adding it to ARC architecture entry

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