spi: Migrate CONFIG_CF_SPI to Kconfig

Signed-off-by: Tuomas Tynkkynen <tuomas@tuxera.com>
diff --git a/configs/M54451EVB_defconfig b/configs/M54451EVB_defconfig
index becd0dd..4b90e01 100644
--- a/configs/M54451EVB_defconfig
+++ b/configs/M54451EVB_defconfig
@@ -22,3 +22,4 @@
 CONFIG_MTD_NOR_FLASH=y
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_STMICRO=y
+CONFIG_CF_SPI=y