ARC: boards: nsim: adjust default testing for better coverage

As of today the build-only testing in upstream is enabled for
nsim_em and nsim_em7d_v22 which are very similar from the
compiler POW. The ARC HS, ARC Secure EM and SMP targets miss
any testing.

So adjust default testing for better coverage by enabling
build-only testing for nsim_hs, nsim_sem and nsim_hs_smp and drop
excessive testing for nsim_em7d_v22.

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

boards/arc/nsim/nsim_em7d_v22.yaml

@@ -6,7 +6,6 @@ arch: arc
 toolchain:
   - zephyr
 testing:
-  default: true
   ignore_tags:
     - net
     - bluetooth

boards/arc/nsim/nsim_hs.yaml

@@ -7,6 +7,7 @@ toolchain:
   - zephyr
   - arcmwdt
 testing:
+  default: true
   ignore_tags:
     - net
     - bluetooth

boards/arc/nsim/nsim_hs_smp.yaml

@@ -7,6 +7,7 @@ toolchain:
   - zephyr
   - arcmwdt
 testing:
+  default: true
   ignore_tags:
     - net
     - bluetooth

boards/arc/nsim/nsim_sem.yaml

@@ -7,6 +7,7 @@ toolchain:
   - zephyr
   - arcmwdt
 testing:
+  default: true
   ignore_tags:
     - net
     - bluetooth