mfd: syscon: atmel-smc: Add new helpers to ease SMC regs manipulation

Add helper functions for atmel Static Memory Controller. The functions
are required to configure SMC. This file is inherited from the work
done by Boris Brezillon for Linux

Signed-off-by: Balamanikandan Gunasundar <balamanikandan.gunasundar@microchip.com>
diff --git a/drivers/Kconfig b/drivers/Kconfig
index 75ac149..9101e53 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -62,6 +62,8 @@
 
 source "drivers/memory/Kconfig"
 
+source "drivers/mfd/Kconfig"
+
 source "drivers/misc/Kconfig"
 
 source "drivers/mmc/Kconfig"