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/thuban_defconfig b/configs/thuban_defconfig
index 5daa63a..b7656d6 100644
--- a/configs/thuban_defconfig
+++ b/configs/thuban_defconfig
@@ -84,6 +84,9 @@
 CONFIG_MMC_OMAP_HS=y
 CONFIG_MTD=y
 CONFIG_MTD_RAW_NAND=y
+CONFIG_SYS_NAND_BLOCK_SIZE=0x20000
+CONFIG_SYS_NAND_PAGE_SIZE=0x800
+CONFIG_SYS_NAND_OOBSIZE=0x40
 CONFIG_DM_SPI_FLASH=y
 CONFIG_SPI_FLASH_WINBOND=y
 CONFIG_MTD_UBI_FASTMAP=y