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/stm32mp15_defconfig b/configs/stm32mp15_defconfig
index 74a7c12..701b151 100644
--- a/configs/stm32mp15_defconfig
+++ b/configs/stm32mp15_defconfig
@@ -92,6 +92,7 @@
 CONFIG_SYS_MTDPARTS_RUNTIME=y
 CONFIG_MTD_RAW_NAND=y
 CONFIG_NAND_STM32_FMC2=y
+CONFIG_SYS_NAND_ONFI_DETECTION=y
 CONFIG_MTD_SPI_NAND=y
 CONFIG_DM_SPI_FLASH=y
 CONFIG_SPI_FLASH_MACRONIX=y