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/marsboard_defconfig b/configs/marsboard_defconfig
index f3e8366..47a32e9 100644
--- a/configs/marsboard_defconfig
+++ b/configs/marsboard_defconfig
@@ -20,6 +20,7 @@
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE=y
 CONFIG_BOARD_EARLY_INIT_F=y
+CONFIG_SYS_MAXARGS=32
 CONFIG_CMD_GPIO=y
 CONFIG_CMD_I2C=y
 CONFIG_CMD_MMC=y