spi/tegra: depend instead of select TEGRA_SYSTEM_DMA

It's unlikely that anyone ever wants to turn off SYSTEM_DMA, but just in
case, it makes more sense to have the driver depend on it than select it.

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index b02920a..a1c468e 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -333,8 +333,7 @@
 
 config SPI_TEGRA
 	tristate "Nvidia Tegra SPI controller"
-	depends on ARCH_TEGRA
-	select TEGRA_SYSTEM_DMA
+	depends on ARCH_TEGRA && TEGRA_SYSTEM_DMA
 	help
 	  SPI driver for NVidia Tegra SoCs