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/warp7_defconfig b/configs/warp7_defconfig
index 5f4f8d0..ab7299c 100644
--- a/configs/warp7_defconfig
+++ b/configs/warp7_defconfig
@@ -15,6 +15,8 @@
 CONFIG_IMX_HAB=y
 CONFIG_SYS_MEMTEST_START=0x80000000
 CONFIG_SYS_MEMTEST_END=0xa0000000
+CONFIG_HAS_BOARD_SIZE_LIMIT=y
+CONFIG_BOARD_SIZE_LIMIT=785408
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_USE_BOOTCOMMAND=y