Convert CONFIG_SPL_NAND_RAW_ONLY et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SPL_NAND_RAW_ONLY
   CONFIG_SPL_NAND_SOFTECC

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/gardena-smart-gateway-at91sam_defconfig b/configs/gardena-smart-gateway-at91sam_defconfig
index 0dbd084..2ee7163 100644
--- a/configs/gardena-smart-gateway-at91sam_defconfig
+++ b/configs/gardena-smart-gateway-at91sam_defconfig
@@ -35,6 +35,7 @@
 CONFIG_SPL_SYS_MALLOC_SIMPLE=y
 # CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_USE_SECTOR is not set
 CONFIG_SPL_NAND_SUPPORT=y
+CONFIG_SPL_NAND_RAW_ONLY=y
 CONFIG_SPL_NAND_DRIVERS=y
 CONFIG_SPL_NAND_BASE=y
 CONFIG_HUSH_PARSER=y