tool: Add a system76_ec command to disable input events

For testing Launch keyboards.

Could easily support in EC firmware as well if we had a use for that,
but not adding that for now.

src/common/include/common/command.h

@@ -44,6 +44,8 @@ enum Command {
     CMD_MATRIX_GET = 17,
     // Save LED settings to ROM
     CMD_LED_SAVE = 18,
+    // Enable/disable no input mode
+    CMD_SET_NO_INPUT = 19,
     //TODO
 };