ppc4xx: Add CONFIG_BOOTP_SUBNETMASK to Sequoia board config

When using dhcp/bootp the "netmask" environment variable is not
set because CONFIG_BOOTP_SUBNETMASK is not defined. But usually this is
desireable, so the following patch adds this this option to the board
config.
Signed-off-by: NMarkus Klotzbuecher <mk@denx.de>
Signed-off-by: NStefan Roese <sr@denx.de>

include/configs/sequoia.h

@@ -329,6 +329,7 @@
 #define CONFIG_BOOTP_BOOTPATH
 #define CONFIG_BOOTP_GATEWAY
 #define CONFIG_BOOTP_HOSTNAME
+#define CONFIG_BOOTP_SUBNETMASK
 
 
 /*