samples: net: openthread: coap: enable NVS as Settings backend

When PSA Crypto API are used they need a PSA ITS implementation and this
is provided by Secure Storage if TF-M is not enabled in the build.
Secure Storage can use Settings as backend and Settings, on its turn, can
use several other backends to store data (ex: ZMS, NVS, etc).
Since NVS is already enabled in other OpenThread Zephyr samples, let's
enable NVS also for this sample.

While at it, also slightly re-organize "sample.yaml" to share more data
between tests and allow building and testing also on the nrf52840dk board.

Signed-off-by: Valerio Setti <[email protected]>

Author: valeriosetti

samples/net/openthread/coap/prj.conf

@@ -26,3 +26,6 @@ CONFIG_OPENTHREAD_XPANID="11:11:11:11:22:22:22:22"
 CONFIG_OPENTHREAD_NETWORKKEY="00:11:22:33:44:55:66:77:88:99:aa:bb:cc:dd:ee:ff"
 CONFIG_OPENTHREAD_CHANNEL=15
 CONFIG_OPENTHREAD_NETWORK_NAME="OpenThreadDemo"
+
+# Use NVS as settings backend
+CONFIG_NVS=y

samples/net/openthread/coap/sample.yaml

@@ -5,17 +5,15 @@ common:
     - openthread
   depends_on: openthread
   min_flash: 140
+  build_only: true
+  platform_allow:
+    - cc1352p7_lp
+    - nrf52840dk/nrf52840
 sample:
   description: Runs the OpenThread stack as FTD with CoAP
   name: OpenThread FTD CoAP
 tests:
-  sample.net.openthread.ftd.coap.client:
-    build_only: true
-    platform_allow:
-      - cc1352p7_lp
+  sample.net.openthread.ftd.coap.client: {}
   sample.net.openthread.ftd.coap.server:
-    build_only: true
-    platform_allow:
-      - cc1352p7_lp
     extra_configs:
       - CONFIG_OT_COAP_SAMPLE_SERVER=y