ppc4xx: Add defines for COM3 & COM4 (UART2 & UART3) on 440EPx/GRx

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/arch/powerpc/include/asm/ppc440epx_grx.h b/arch/powerpc/include/asm/ppc440epx_grx.h
index 252f35b..6c21472 100644
--- a/arch/powerpc/include/asm/ppc440epx_grx.h
+++ b/arch/powerpc/include/asm/ppc440epx_grx.h
@@ -36,6 +36,8 @@
 
 #define CONFIG_SYS_NS16550_COM1	(CONFIG_SYS_PERIPHERAL_BASE + 0x0300)
 #define CONFIG_SYS_NS16550_COM2	(CONFIG_SYS_PERIPHERAL_BASE + 0x0400)
+#define CONFIG_SYS_NS16550_COM3	(CONFIG_SYS_PERIPHERAL_BASE + 0x0500)
+#define CONFIG_SYS_NS16550_COM4	(CONFIG_SYS_PERIPHERAL_BASE + 0x0600)
 
 #define GPIO0_BASE		(CONFIG_SYS_PERIPHERAL_BASE + 0x0b00)
 #define GPIO1_BASE		(CONFIG_SYS_PERIPHERAL_BASE + 0x0c00)