spi: tegra: add spi driver for sflash controller

NVIDIA's Tegra20 have the SPI (SFLASH) controller to
interface with spi flash device which is used for system
boot. Add the spi driver for this controller.
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

Documentation/devicetree/bindings/spi/nvidia,tegra20-sflash.txt

+NVIDIA Tegra20 SFLASH controller.
+
+Required properties:
+- compatible : should be "nvidia,tegra20-sflash".
+- reg: Should contain SFLASH registers location and length.
+- interrupts: Should contain SFLASH interrupts.
+- nvidia,dma-request-selector : The Tegra DMA controller's phandle and
+  request selector for this SFLASH controller.
+
+Recommended properties:
+- spi-max-frequency: Definition as per
+                     Documentation/devicetree/bindings/spi/spi-bus.txt
+
+Example:
+
+spi@7000d600 {
+	compatible = "nvidia,tegra20-sflash";
+	reg = <0x7000c380 0x80>;
+	interrupts = <0 39 0x04>;
+	nvidia,dma-request-selector = <&apbdma 16>;
+	spi-max-frequency = <25000000>;
+	#address-cells = <1>;
+	#size-cells = <0>;
+	status = "disabled";
+};
+

drivers/spi/Kconfig

@@ -385,6 +385,14 @@ config SPI_MXS
 	help
 	  SPI driver for Freescale MXS devices.
 
+config SPI_TEGRA20_SFLASH
+	tristate "Nvidia Tegra20 Serial flash Controller"
+	depends on ARCH_TEGRA
+	help
+	  SPI driver for Nvidia Tegra20 Serial flash Controller interface.
+	  The main usecase of this controller is to use spi flash as boot
+	  device.
+
 config SPI_TEGRA20_SLINK
 	tristate "Nvidia Tegra20/Tegra30 SLINK Controller"
 	depends on ARCH_TEGRA && TEGRA20_APB_DMA

drivers/spi/Makefile

@@ -60,6 +60,7 @@ obj-$(CONFIG_SPI_SH_MSIOF)		+= spi-sh-msiof.o
 obj-$(CONFIG_SPI_SH_SCI)		+= spi-sh-sci.o
 obj-$(CONFIG_SPI_SIRF)		+= spi-sirf.o
 obj-$(CONFIG_SPI_STMP3XXX)		+= spi-stmp.o
+obj-$(CONFIG_SPI_TEGRA20_SFLASH)	+= spi-tegra20-sflash.o
 obj-$(CONFIG_SPI_TEGRA20_SLINK)		+= spi-tegra20-slink.o
 obj-$(CONFIG_SPI_TI_SSP)		+= spi-ti-ssp.o
 obj-$(CONFIG_SPI_TLE62X0)		+= spi-tle62x0.o