Convert CONFIG_SYS_NAND_ONFI_DETECTION to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_NAND_ONFI_DETECTION

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/plutux_defconfig b/configs/plutux_defconfig
index 4000de1..fc339d5 100644
--- a/configs/plutux_defconfig
+++ b/configs/plutux_defconfig
@@ -31,6 +31,7 @@
 CONFIG_SPL_DM=y
 CONFIG_MTD=y
 CONFIG_MTD_RAW_NAND=y
+CONFIG_SYS_NAND_ONFI_DETECTION=y
 CONFIG_SYS_NS16550=y
 CONFIG_USB=y
 CONFIG_USB_EHCI_HCD=y