ARC: nsim_nsim_hs_mpuv6: add missing defconfig

After recent HWv2 model there is defconfig file
missing, so we got incorrect platform configuration. Fix that.

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