samples: audio: sof: add filter

Build only for relevant platforms.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>
diff --git a/samples/audio/sof/sample.yaml b/samples/audio/sof/sample.yaml
index 32ba0df..2ccc2bc 100644
--- a/samples/audio/sof/sample.yaml
+++ b/samples/audio/sof/sample.yaml
@@ -7,5 +7,6 @@
   sample.audio.sof:
     tags: sof
     build_only: true
+    platform_allow: intel_adsp_cavs15 intel_adsp_cavs18 intel_adsp_cavs20
     integration_platforms:
       - intel_adsp_cavs15