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/nas220_defconfig b/configs/nas220_defconfig
index 924061d..a3129fb 100644
--- a/configs/nas220_defconfig
+++ b/configs/nas220_defconfig
@@ -20,6 +20,7 @@
 CONFIG_RESET_PHY_R=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="nas220> "
+CONFIG_SYS_MAXARGS=32
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_IDE=y
 CONFIG_CMD_NAND=y