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/sama5d3xek_mmc_defconfig b/configs/sama5d3xek_mmc_defconfig
index e1a8ab7..a39743f 100644
--- a/configs/sama5d3xek_mmc_defconfig
+++ b/configs/sama5d3xek_mmc_defconfig
@@ -73,6 +73,7 @@
 CONFIG_NAND_ATMEL=y
 CONFIG_ATMEL_NAND_HW_PMECC=y
 CONFIG_PMECC_CAP=4
+CONFIG_SYS_NAND_ONFI_DETECTION=y
 CONFIG_DM_SPI_FLASH=y
 CONFIG_SF_DEFAULT_SPEED=30000000
 CONFIG_SPI_FLASH_ATMEL=y