spi: Migrate CONFIG_SH_SPI to Kconfig

Signed-off-by: Tuomas Tynkkynen <tuomas@tuxera.com>
diff --git a/configs/sh7752evb_defconfig b/configs/sh7752evb_defconfig
index 3d68122..db46097 100644
--- a/configs/sh7752evb_defconfig
+++ b/configs/sh7752evb_defconfig
@@ -37,4 +37,5 @@
 CONFIG_NETDEVICES=y
 CONFIG_SH_ETHER=y
 CONFIG_SCIF_CONSOLE=y
+CONFIG_SH_SPI=y
 CONFIG_USE_PRIVATE_LIBGCC=y