Convert CONFIG_SPL_NAND_LOAD et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SPL_NAND_LOAD
   CONFIG_SYS_NAND_BLOCK_SIZE
   CONFIG_SYS_NAND_PAGE_SIZE
   CONFIG_SYS_NAND_OOBSIZE

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 4e1b44e..20ef4ef 100644
--- a/configs/gardena-smart-gateway-at91sam_defconfig
+++ b/configs/gardena-smart-gateway-at91sam_defconfig
@@ -87,6 +87,9 @@
 CONFIG_NAND_ATMEL=y
 CONFIG_SPL_GENERATE_ATMEL_PMECC_HEADER=y
 CONFIG_MTD_UBI_FASTMAP=y
+CONFIG_SYS_NAND_BLOCK_SIZE=0x20000
+CONFIG_SYS_NAND_PAGE_SIZE=0x800
+CONFIG_SYS_NAND_OOBSIZE=0x40
 CONFIG_DM_ETH=y
 CONFIG_MACB=y
 CONFIG_PINCTRL=y