Convert CONFIG_SYS_NAND_MAX_OOBFREE et al to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_NAND_MAX_OOBFREE
   CONFIG_SYS_NAND_MAX_ECCPOS

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/am3517_evm_defconfig b/configs/am3517_evm_defconfig
index 45332e2..0839d36 100644
--- a/configs/am3517_evm_defconfig
+++ b/configs/am3517_evm_defconfig
@@ -81,6 +81,8 @@
 CONFIG_SYS_NAND_BUSWIDTH_16BIT=y
 CONFIG_SYS_NAND_U_BOOT_LOCATIONS=y
 CONFIG_SYS_NAND_U_BOOT_OFFS=0x80000
+CONFIG_SYS_NAND_MAX_OOBFREE=2
+CONFIG_SYS_NAND_MAX_ECCPOS=56
 CONFIG_MII=y
 CONFIG_DRIVER_TI_EMAC=y
 CONFIG_DRIVER_TI_EMAC_USE_RMII=y