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/P2020RDB-PC_NAND_defconfig b/configs/P2020RDB-PC_NAND_defconfig
index 3b57b0c..89294ac 100644
--- a/configs/P2020RDB-PC_NAND_defconfig
+++ b/configs/P2020RDB-PC_NAND_defconfig
@@ -72,6 +72,7 @@
 CONFIG_FLASH_CFI_MTD=y
 CONFIG_SYS_FLASH_CFI=y
 CONFIG_MTD_RAW_NAND=y
+CONFIG_SYS_NAND_BLOCK_SIZE=0x4000
 CONFIG_DM_SPI_FLASH=y
 CONFIG_SF_DEFAULT_MODE=0
 CONFIG_SF_DEFAULT_SPEED=10000000