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/tuxx1_defconfig b/configs/tuxx1_defconfig
index c253664..9c865c1 100644
--- a/configs/tuxx1_defconfig
+++ b/configs/tuxx1_defconfig
@@ -153,6 +153,7 @@
 CONFIG_LAST_STAGE_INIT=y
 CONFIG_MISC_INIT_R=y
 CONFIG_HUSH_PARSER=y
+CONFIG_SYS_MAXARGS=32
 CONFIG_CMD_IMLS=y
 CONFIG_CMD_ASKENV=y
 CONFIG_CMD_GREPENV=y