- simple_display: avoid compiler warning

Signed-off-by: Thilo Graf <dbt@novatux.de>

src/driver/simple_display.cpp

@@ -554,6 +554,8 @@ void CLCD::setBrightness(int dimm)
 	if (pfd)
 		write(pfd, value.c_str(), value.length());
 	close(pfd);
+#else
+	(void)dimm; // avoid compiler warning
 #endif
 }