serial: Support serial multi for Microblaze

enable serial multi for Microblaze.

Signed-off-by: Michal Simek <monstr@monstr.eu>
Acked-by: Stephan Linz <linz@li-pro.net>

include/serial.h

@@ -31,7 +31,8 @@ extern struct serial_device *default_serial_console(void);
 	defined(CONFIG_MB86R0x) || defined(CONFIG_MPC5xxx) || \
 	defined(CONFIG_MPC83xx) || defined(CONFIG_MPC85xx) || \
 	defined(CONFIG_MPC86xx) || defined(CONFIG_SYS_SC520) || \
-	defined(CONFIG_TEGRA20) || defined(CONFIG_SYS_COREBOOT)
+	defined(CONFIG_TEGRA20) || defined(CONFIG_SYS_COREBOOT) || \
+	defined(CONFIG_MICROBLAZE)
 extern struct serial_device serial0_device;
 extern struct serial_device serial1_device;
 #if defined(CONFIG_SYS_NS16550_SERIAL)