ARC: boards: nsim: don't set ARC_HAS_ACCL_REGS to it's default

Don't setup CONFIG_ARC_HAS_ACCL_REGS option for board explicitly
if we use it default value.

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