spi: npcm-fiu: add NPCM7xx FIU controller driver

Add Nuvoton NPCM BMC Flash Interface Unit(FIU) SPI master
controller driver using SPI-MEM interface.

The FIU supports single, dual or quad communication interface.
The FIU controller driver provides flash access in UMA(User
Mode Access) mode by using an indirect address/data mechanism.

the dts node is followed upstream kernel dts name.

Signed-off-by: Jim Liu <JJLIU0@nuvoton.com>
Signed-off-by: Stanley Chu <yschu@nuvoton.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
[Jagan: fixed the Kconfig, Makefile order]
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 8dba95a..a1e515c 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -283,6 +283,12 @@
 	  can be used to access the SPI flash on platforms embedding
 	  this Macronix IP core.
 
+config NPCM_FIU_SPI
+	bool "FIU driver for Nuvoton NPCM SoC"
+	help
+	  This enables support for the Flash Interface Unit SPI controller
+	  in master mode.
+
 config NXP_FSPI
 	bool "NXP FlexSPI driver"
 	depends on SPI_MEM