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/NX823.h b/include/configs/NX823.h
index 524aa06..da1c173 100644
--- a/include/configs/NX823.h
+++ b/include/configs/NX823.h
@@ -47,7 +47,7 @@
 #undef	CONFIG_8xx_CONS_NONE
 #define CONFIG_BAUDRATE 57600	/* console baudrate = 115kbps	*/
 #define CONFIG_BOOTDELAY	2	/* autoboot after 2 seconds */
-#define CONFIG_BOOTARGS		"ramdisk=8000 "\
+#define CONFIG_BOOTARGS		"ramdisk_size=8000 "\
 				"root=/dev/nfs rw nfsroot=10.77.77.250:/ppcroot "\
 				"nfsaddrs=10.77.77.20:10.77.77.250"
 #define CONFIG_BOOTCOMMAND	"bootm 400e0000"