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>
diff --git a/configs/integratorcp_cm920t_defconfig b/configs/integratorcp_cm920t_defconfig
index 7585d6d..19c72c7 100644
--- a/configs/integratorcp_cm920t_defconfig
+++ b/configs/integratorcp_cm920t_defconfig
@@ -12,6 +12,7 @@
 CONFIG_ENV_ADDR=0x24F00000
 CONFIG_HAS_CUSTOM_SYS_INIT_SP_ADDR=y
 CONFIG_CUSTOM_SYS_INIT_SP_ADDR=0x7ffff20
+CONFIG_SYS_MONITOR_LEN=1048576
 CONFIG_SYS_MONITOR_BASE=0x27F40000
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="root=/dev/mtdblock0 console=ttyAMA0 console=tty ip=dhcp netdev=27,0,0xfc800000,0xfc800010,eth0 video=clcdfb:0"