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/mx7ulp_com_defconfig b/configs/mx7ulp_com_defconfig
index 2f860f6..4e51a79 100644
--- a/configs/mx7ulp_com_defconfig
+++ b/configs/mx7ulp_com_defconfig
@@ -9,6 +9,8 @@
 CONFIG_DEFAULT_DEVICE_TREE="imx7ulp-com"
 CONFIG_LDO_ENABLED_MODE=y
 CONFIG_TARGET_MX7ULP_COM=y
+CONFIG_HAS_BOARD_SIZE_LIMIT=y
+CONFIG_BOARD_SIZE_LIMIT=785408
 CONFIG_SYS_LOAD_ADDR=0x60800000
 CONFIG_USE_BOOTCOMMAND=y
 CONFIG_BOOTCOMMAND="if run loadimage; then run mmcboot; fi"