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/at91sam9n12ek_nandflash_defconfig b/configs/at91sam9n12ek_nandflash_defconfig
index ab51b70..b67cc57 100644
--- a/configs/at91sam9n12ek_nandflash_defconfig
+++ b/configs/at91sam9n12ek_nandflash_defconfig
@@ -43,6 +43,8 @@
 CONFIG_MTD=y
 CONFIG_NAND_ATMEL=y
 CONFIG_SPL_GENERATE_ATMEL_PMECC_HEADER=y
+CONFIG_SYS_NAND_PAGE_SIZE=0x800
+CONFIG_SYS_NAND_OOBSIZE=0x40
 CONFIG_DM_SPI_FLASH=y
 CONFIG_SF_DEFAULT_SPEED=30000000
 CONFIG_SPI_FLASH_ATMEL=y