dhcp: Fix constants in different bank from code

Signed-off-by: João Silva <jgc3silva@gmail.com>

dhcp.c

@@ -51,7 +51,7 @@ __xdata uip_ipaddr_t server;
 #define DHCP_END		255
 
 #pragma codeseg BANK3
-#pragma constseg BANK2
+#pragma constseg BANK3
 
 struct dhcp_pkt {
 	uint8_t type;