Replace deprecated "ramdisk" with "ramdisk_size" kernel parameter.

The Linux commit fac8b209b1084bc85748bd54e13d00c1262b220f ("Remove
final traces of long-deprecated "ramdisk" kernel parm") makes these
changes neccessary.

Signed-off-by: Detlev Zundel <dzu@denx.de>
diff --git a/include/configs/zeus.h b/include/configs/zeus.h
index 810a528..cd120df 100644
--- a/include/configs/zeus.h
+++ b/include/configs/zeus.h
@@ -333,7 +333,7 @@
 	"nfsargs=setenv bootargs root=/dev/nfs rw"			\
 		" nfsroot=${serverip}:${rootpath}\0"			\
 	"ramargs=setenv bootargs root=/dev/ram rw"			\
-		" ramdisk=${ramdisk_size}\0"				\
+		" ramdisk_size=${ramdisk_size}\0"			\
 	"addip=setenv bootargs ${bootargs} "				\
 		"ip=${ipaddr}:${serverip}:${gatewayip}:${netmask}"	\
 	        ":${hostname}:${netdev}:off panic=1\0"			\