arm/ls102xa:add hwconfig setting to support disable unused devices

DEVDISRn registers provides a mechanism for gating clocks of IP blocks
that are not used. Here we implement hwconfig option to allow users
to disable unused peripherals on the board.

For ex. If eSDHC/qDMA/eDMA are unused and with disabled status in dts,
User can enable CONFIG_FSL_DEVICE_DISABLE and set "devdis:esdhc,qdma,edma"
in hwconfig, thus ESDHC controller & eDMA/qDMA will be clock gated to
save more power.

Signed-off-by: Zhuoyu Zhang <Zhuoyu.Zhang@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>
diff --git a/include/configs/ls1021aqds.h b/include/configs/ls1021aqds.h
index dfaffa1..b44f326 100644
--- a/include/configs/ls1021aqds.h
+++ b/include/configs/ls1021aqds.h
@@ -566,7 +566,9 @@
 #define CONFIG_TIMER_CLK_FREQ		12500000
 
 #define CONFIG_HWCONFIG
-#define HWCONFIG_BUFFER_SIZE		128
+#define HWCONFIG_BUFFER_SIZE		256
+
+#define CONFIG_FSL_DEVICE_DISABLE
 
 #define CONFIG_BOOTDELAY		3