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>

include/fsl_devdis.h

@@ -0,0 +1,18 @@
+/*
+ * Copyright 2015 Freescale Semiconductor, Inc.
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#ifndef __FSL_DEVDIS_H_
+#define __FSL_DEVDIS_H_
+
+struct devdis_table {
+	char name[32];
+	u32 offset;
+	u32 mask;
+};
+
+void device_disable(const struct devdis_table *tbl, uint32_t num);
+
+#endif