spi: Kconfig: Enable SPI_SUNXI for SUNXI

SPI_SUNXI driver is fully dm-aware and the Allwinner
architecture kconfig would have logic to enable the
DM_SPI. So, select default spi sunxi driver for
sunxi architecture.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 0152dff..7be867d 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -260,6 +260,7 @@
 
 config SPI_SUNXI
 	bool "Allwinner SoC SPI controllers"
+	default ARCH_SUNXI
 	help
 	  Enable the Allwinner SoC SPi controller driver.