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/pg_wcom_expu1_update_defconfig b/configs/pg_wcom_expu1_update_defconfig
index bea61f7..e237a64 100644
--- a/configs/pg_wcom_expu1_update_defconfig
+++ b/configs/pg_wcom_expu1_update_defconfig
@@ -39,6 +39,7 @@
 CONFIG_EVENT=y
 CONFIG_LAST_STAGE_INIT=y
 CONFIG_MISC_INIT_R=y
+CONFIG_SYS_MAXARGS=32
 CONFIG_CMD_IMLS=y
 CONFIG_CMD_GREPENV=y
 CONFIG_CMD_MEMINFO=y