dm: at91: Add driver model support for the spi driver

Add driver model support while retaining the existing legacy code.
This allows the driver to support boards that have converted to
driver model as well as those that have not.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Stephen Warren <swarren@nvidia.com>
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 8724f87..0f51b3a 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -32,6 +32,14 @@
 	  uses driver model and requires a device tree binding to operate.
 	  please refer to doc/device-tree-bindings/spi/spi-ath79.txt.
 
+config ATMEL_SPI
+	bool "Atmel SPI driver"
+	depends on ARCH_AT91
+	help
+	  This enables driver for the Atmel SPI Controller, present on
+	  many AT32 (AVR32) and AT91 (ARM) chips. This driver can be
+	  used to access the SPI Flash, such as AT25DF321.
+
 config CADENCE_QSPI
 	bool "Cadence QSPI driver"
 	help