tests: add a new harness keyword to schema

This keyword would mean that a special harness is needed to run the
tests sucessfully. This can be as simple as a loopback wiring or a
complete hardware test setup for sensor and IO testing. It is free form
initially and would be changed to be an enum once we have more values in
place.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>
diff --git a/scripts/sanitycheck b/scripts/sanitycheck
index 1cac0be..0700288 100755
--- a/scripts/sanitycheck
+++ b/scripts/sanitycheck
@@ -1078,7 +1078,9 @@
                        "platform_whitelist": {"type": "set"},
                        "toolchain_exclude": {"type": "set"},
                        "toolchain_whitelist": {"type": "set"},
-                       "filter": {"type": "str"}}
+                       "filter": {"type": "str"},
+                       "harness": {"type": "str"}
+                       }
 
 
 class SanityConfigParser: