New behavior for ext power control

app/include/dt-bindings/zmk/ext_power.h

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#define EXT_POWER_OFF_CMD 0
+#define EXT_POWER_ON_CMD 1
+
+/*
+ * Note: Some future commands might include additional parameters, so we
+ * defines these aliases up front.
+ */
+
+#define EP_ON EXT_POWER_ON_CMD 0
+#define EP_OFF EXT_POWER_OFF_CMD 0