Allow this to be unset, such that gd->mon_len is invalid. This seems to be
what the sh architecture does.
Signed-off-by: Simon Glass <sjg@chromium.org>
gd->mon_len = CONFIG_SYS_MONITOR_LEN;
#elif defined(CONFIG_NDS32)
gd->mon_len = (ulong)(&__bss_end) - (ulong)(&_start);
-#else
+#elif defined(CONFIG_SYS_MONITOR_BASE)
/* TODO: use (ulong)&__bss_end - (ulong)&__text_start; ? */
gd->mon_len = (ulong)&__bss_end - CONFIG_SYS_MONITOR_BASE;
#endif