spi/sirf: Depends on SIRF_DMA

Now that DMA support has been added to the driver it needs the
architecture DMA driver to be built in order to link.
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/spi/Kconfig

@@ -404,7 +404,7 @@ config SPI_SH_HSPI
 
 config SPI_SIRF
 	tristate "CSR SiRFprimaII SPI controller"
-	depends on ARCH_SIRF
+	depends on SIRF_DMA
 	select SPI_BITBANG
 	help
 	  SPI driver for CSR SiRFprimaII SoCs