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/sam9x60ek_mmc_defconfig b/configs/sam9x60ek_mmc_defconfig
index 178f113..fd6f89a 100644
--- a/configs/sam9x60ek_mmc_defconfig
+++ b/configs/sam9x60ek_mmc_defconfig
@@ -60,6 +60,7 @@
 CONFIG_NAND_ATMEL=y
 CONFIG_ATMEL_NAND_HW_PMECC=y
 CONFIG_PMECC_CAP=8
+CONFIG_SYS_NAND_ONFI_DETECTION=y
 CONFIG_PHY_MICREL=y
 CONFIG_DM_ETH=y
 CONFIG_MACB=y