spi: add spi_tegra driver

v2 changes:
  from Thierry Reding:
    * add "select TEGRA_SYSTEM_DMA" to Kconfig
  from Grant Likely:
    * add oneline description to header
    * inline references to DRIVER_NAME
    * inline references to BUSY_TIMEOUT
    * open coded bytes_per_word()
    * spi_readl/writel -> spi_tegra_readl/writel
    * move transfer validation to spi_tegra_transfer
    * don't request_mem_region iomem as platform bus does that for us
    * __exit -> __devexit

v3 changes:
  from Russell King:
    * put request_mem_region back int
  from Grant Likely:
    * remove #undef DEBUG
    * add SLINK_ to register bit defines
    * remove unused bytes_per_word
    * make spi_tegra_readl/writel static linine
    * various refactoring for clarity
    * mark err if BSY bit is not cleared after 1000 retries
    * move spinlock to protect setting of RDY bit
    * subsys_initcall -> module_init

v3 changes:
  from Grant Likely:
    * update spi_tegra to use PTR_ERRless dma API

v4 changes:
  from Grant Likely:
    * remove empty spi_tegra_cleanup fucntion
    * allow device ids of -1
Signed-off-by: Erik Gilling <konkers@android.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Thierry Reding <thierry.reding@avionic-design.de>
Cc: Russell King <linux@arm.linux.org.uk>

spi: tegra: cleanups from upstream review

Change-Id: Icecf7e64efcb39de072a15234ba1faa4bad40d25
Signed-off-by: Erik Gilling <konkers@android.com>

drivers/spi/Kconfig

@@ -329,6 +329,13 @@ config SPI_STMP3XXX
 	help
 	  SPI driver for Freescale STMP37xx/378x SoC SSP interface
 
+config SPI_TEGRA
+	tristate "Nvidia Tegra SPI controller"
+	depends on ARCH_TEGRA
+	select TEGRA_SYSTEM_DMA
+	help
+	  SPI driver for NVidia Tegra SoCs
+
 config SPI_TOPCLIFF_PCH
 	tristate "Topcliff PCH SPI Controller"
 	depends on PCI

drivers/spi/Makefile

@@ -39,6 +39,7 @@ obj-$(CONFIG_SPI_PPC4xx)		+= spi_ppc4xx.o
 obj-$(CONFIG_SPI_S3C24XX_GPIO)		+= spi_s3c24xx_gpio.o
 obj-$(CONFIG_SPI_S3C24XX)		+= spi_s3c24xx_hw.o
 obj-$(CONFIG_SPI_S3C64XX)		+= spi_s3c64xx.o
+obj-$(CONFIG_SPI_TEGRA)			+= spi_tegra.o
 obj-$(CONFIG_SPI_TOPCLIFF_PCH)		+= spi_topcliff_pch.o
 obj-$(CONFIG_SPI_TXX9)			+= spi_txx9.o
 obj-$(CONFIG_SPI_XILINX)		+= xilinx_spi.o