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>

drivers/misc/fsl_devdis.c

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2015 Freescale Semiconductor, Inc.
+ * Author: Zhuoyu Zhang <Zhuoyu.Zhang@freescale.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+#include <common.h>
+#include <asm/io.h>
+#include <asm/arch-ls102xa/immap_ls102xa.h>
+#include <asm/arch-ls102xa/config.h>
+#include <linux/compiler.h>
+#include <hwconfig.h>
+#include <fsl_devdis.h>
+
+void device_disable(const struct devdis_table *tbl, uint32_t num)
+{
+	int i;
+	struct ccsr_gur __iomem *gur = (void *)CONFIG_SYS_FSL_GUTS_ADDR;
+
+	/*
+	 * Extract hwconfig from environment and disable unused device.
+	 */
+	for (i = 0; i < num; i++) {
+		if (hwconfig_sub("devdis", tbl[i].name))
+			setbits_be32(&gur->devdisr + tbl[i].offset,
+				tbl[i].mask);
+	}
+}
+