display5: Add missing environment.h include to avoid warning

Without this change the following warning shows up when building:

board/liebherr/display5/display5.c:270:3:
warning: implicit declaration of function ‘eth_env_set_enetaddr’ [-Wimplicit-function-declaration]

This commit fixes this issue.
Signed-off-by: NLukasz Majewski <lukma@denx.de>

board/liebherr/display5/display5.c

@@ -25,6 +25,7 @@
 #include <miiphy.h>
 #include <netdev.h>
 #include <i2c.h>
+#include <environment.h>
 
 #include <dm.h>
 #include <dm/platform_data/serial_mxc.h>