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/tbs2910_defconfig b/configs/tbs2910_defconfig
index 4d6ca4f..993997b 100644
--- a/configs/tbs2910_defconfig
+++ b/configs/tbs2910_defconfig
@@ -15,6 +15,8 @@
 CONFIG_SYS_MEMTEST_START=0x10000000
 CONFIG_SYS_MEMTEST_END=0x2f400000
 CONFIG_LTO=y
+CONFIG_HAS_BOARD_SIZE_LIMIT=y
+CONFIG_BOARD_SIZE_LIMIT=392192
 CONFIG_SUPPORT_RAW_INITRD=y
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTCOMMAND=y