Fix implicit-fallthrough warnings.

Test: make checkbuild
Bug: 112564944
Change-Id: Ifc8b7444b95d667b0d185c7d45b3f15278d4af2f
diff --git a/broadcastradio/common/utils2x/Utils.cpp b/broadcastradio/common/utils2x/Utils.cpp
index 3e20b35..f292c08 100644
--- a/broadcastradio/common/utils2x/Utils.cpp
+++ b/broadcastradio/common/utils2x/Utils.cpp
@@ -215,7 +215,7 @@
             break;
         case IdentifierType::DAB_FREQUENCY:
             expect(val > 100000u, "f > 100MHz");
-        // fallthrough
+            [[fallthrough]];
         case IdentifierType::AMFM_FREQUENCY:
         case IdentifierType::DRMO_FREQUENCY:
             expect(val > 100u, "f > 100kHz");