spi: Migrate CONFIG_MXC_SPI to Kconfig

Signed-off-by: Tuomas Tynkkynen <tuomas@tuxera.com>
diff --git a/configs/mx35pdk_defconfig b/configs/mx35pdk_defconfig
index a9787eb..ac70e8e 100644
--- a/configs/mx35pdk_defconfig
+++ b/configs/mx35pdk_defconfig
@@ -31,6 +31,7 @@
 CONFIG_NETDEVICES=y
 CONFIG_SMC911X=y
 CONFIG_SMC911X_BASE=0xB6000000
+CONFIG_MXC_SPI=y
 CONFIG_USB=y
 CONFIG_USB_EHCI_HCD=y
 CONFIG_USB_STORAGE=y