Convert CONFIG_SYS_MONITOR_LEN to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_MONITOR_LEN

To do this, we set a default of 0 for everyone because there are a
number of cases where we define CONFIG_SYS_MONITOR_LEN but the only
impact is that we set TOTAL_MALLOC_LEN to be CONFIG_SYS_MALLOC_LEN +
CONFIG_ENV_SIZE, so we must continue to allow all boards to set this
value. Update the SPL code to use 200 KB as the default raw U-Boot size
directly, if we don't have a real CONFIG_SYS_MONITOR_LEN value.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

Kconfig

@@ -583,6 +583,17 @@ config SYS_SRAM_SIZE
 	default 0x10000 if TARGET_TRICORDER
 	default 0x0
 
+config SYS_MONITOR_LEN
+	int "Maximum size in bytes reserved for U-Boot in memory"
+	default 1048576 if X86
+	default 0
+	help
+	  Size of memory reserved for monitor code, used to determine
+	  _at_compile_time_ (!) if the environment is embedded within the
+	  U-Boot image, or in a separate flash sector, among other uses where
+	  we need to set a maximum size of the U-Boot binary itself that will
+	  be loaded.
+
 config MP
 	bool "Support for multiprocessor"
 	help