spi: Migrate CONFIG_SH_SPI to Kconfig

Signed-off-by: Tuomas Tynkkynen <tuomas@tuxera.com>
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index 1e95dc4..3d2cd2d 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -239,6 +239,12 @@
 	help
 	  Enable the Davinci SPI driver
 
+config SH_SPI
+	bool "SuperH SPI driver"
+	help
+	  Enable the SuperH SPI controller driver. This driver can be used
+	  on various SuperH SoCs, such as SH7757.
+
 config TI_QSPI
 	bool "TI QSPI driver"
 	help