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/bcm968580xref_ram_defconfig b/configs/bcm968580xref_ram_defconfig
index c5ab976..b43396f 100644
--- a/configs/bcm968580xref_ram_defconfig
+++ b/configs/bcm968580xref_ram_defconfig
@@ -40,6 +40,7 @@
 CONFIG_MTD_RAW_NAND=y
 CONFIG_NAND_BRCMNAND=y
 CONFIG_NAND_BRCMNAND_6858=y
+CONFIG_SYS_NAND_ONFI_DETECTION=y
 CONFIG_DM_SPI_FLASH=y
 CONFIG_SPI_FLASH_SFDP_SUPPORT=y
 CONFIG_SPI_FLASH_MACRONIX=y