tests: posix: common: test userspace as well

Ensure that userspace is tested in the common posix testsuite.

Signed-off-by: Chris Friedt <[email protected]>

Author: cfriedt

tests/posix/common/testcase.yaml

@@ -71,3 +71,9 @@ tests:
     extra_configs:
       - CONFIG_DYNAMIC_THREAD=n
       - CONFIG_THREAD_STACK_INFO=n
+  portability.posix.common.userspace:
+    filter: CONFIG_ARCH_HAS_USERSPACE
+    tags:
+      - userspace
+    extra_configs:
+      - CONFIG_USERSPACE=y