powerpc/t1023rdb: change default core frequency to 1200MHz

Per new requirement, change default core frequency
from previous 1400MHz to 1200MHz to save power.

Signed-off-by: Shengzhou Liu <Shengzhou.Liu@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>

board/freescale/t102xrdb/t1023_rcw.cfg

@@ -1,8 +1,8 @@
 #PBL preamble and RCW header for T1023RDB
 aa55aa55 010e0100
 #SerDes Protocol: 0x77
-#Core/DDR: 1400Mhz/1600MT/s with single source clock
-0810000e 00000000 00000000 00000000
+#Default Core=1200MHz, DDR=1600MT/s with single source clock
+0810000c 00000000 00000000 00000000
 3b800003 00000012 e8104000 21000000
 00000000 00000000 00000000 00022800
 00000130 04020200 00000000 00000006