fix(sensors): Only accept data once per behavior.

* Don't accept data for the same behavior on multiple layers more than
  once, to avoid duplicate/extraneous triggers.

app/include/zmk/keymap.h

@@ -8,6 +8,10 @@
 
 #include <zmk/events/position_state_changed.h>
 
+#define ZMK_LAYER_CHILD_LEN_PLUS_ONE(node) 1 +
+#define ZMK_KEYMAP_LAYERS_LEN                                                                      \
+    (DT_FOREACH_CHILD(DT_INST(0, zmk_keymap), ZMK_LAYER_CHILD_LEN_PLUS_ONE) 0)
+
 typedef uint32_t zmk_keymap_layers_state_t;
 
 uint8_t zmk_keymap_layer_default();