Convert CONFIG_BOARD_SIZE_LIMIT to Kconfig

This converts the following to Kconfig:
   CONFIG_BOARD_SIZE_LIMIT

To do this, introduce CONFIG_HAS_BOARD_SIZE_LIMIT.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/vf610twr_defconfig b/configs/vf610twr_defconfig
index 787ce4d..4d2aaee 100644
--- a/configs/vf610twr_defconfig
+++ b/configs/vf610twr_defconfig
@@ -13,6 +13,8 @@
 CONFIG_DEFAULT_DEVICE_TREE="vf610-twr"
 CONFIG_SYS_MEMTEST_START=0x80010000
 CONFIG_SYS_MEMTEST_END=0x87c00000
+CONFIG_HAS_BOARD_SIZE_LIMIT=y
+CONFIG_BOARD_SIZE_LIMIT=520192
 CONFIG_SYS_LOAD_ADDR=0x82000000
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTCOMMAND=y