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/am335x_guardian_defconfig b/configs/am335x_guardian_defconfig
index 93218dd..272d5b8 100644
--- a/configs/am335x_guardian_defconfig
+++ b/configs/am335x_guardian_defconfig
@@ -89,6 +89,7 @@
 CONFIG_DM_MTD=y
 CONFIG_MTD_RAW_NAND=y
 CONFIG_SYS_NAND_BLOCK_SIZE=0x40000
+CONFIG_SYS_NAND_ONFI_DETECTION=y
 CONFIG_SYS_NAND_PAGE_COUNT=0x40
 CONFIG_SYS_NAND_PAGE_SIZE=0x1000
 CONFIG_SYS_NAND_OOBSIZE=0x100