Convert CONFIG_SYS_MAXARGS to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_MAXARGS

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/rastaban_defconfig b/configs/rastaban_defconfig
index 4bdaae0..2f10ad0 100644
--- a/configs/rastaban_defconfig
+++ b/configs/rastaban_defconfig
@@ -46,6 +46,7 @@
 # CONFIG_SPL_AM33XX_ENABLE_RTC32K_OSC is not set
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="U-Boot# "
+CONFIG_SYS_MAXARGS=32
 CONFIG_CMD_ASKENV=y
 CONFIG_CMD_DFU=y
 # CONFIG_CMD_FLASH is not set