spi: Migrate CONFIG_KIRKWOOD_SPI to Kconfig

Signed-off-by: Tuomas Tynkkynen <tuomas@tuxera.com>
diff --git a/configs/ds414_defconfig b/configs/ds414_defconfig
index ef55ff6..5d1d6ab 100644
--- a/configs/ds414_defconfig
+++ b/configs/ds414_defconfig
@@ -46,6 +46,7 @@
 CONFIG_DEBUG_UART_CLOCK=250000000
 CONFIG_DEBUG_UART_SHIFT=2
 CONFIG_SYS_NS16550=y
+CONFIG_KIRKWOOD_SPI=y
 CONFIG_USB=y
 CONFIG_DM_USB=y
 CONFIG_USB_EHCI_HCD=y