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/dragonboard820c_defconfig b/configs/dragonboard820c_defconfig
index 3bd22aa..58e3f03 100644
--- a/configs/dragonboard820c_defconfig
+++ b/configs/dragonboard820c_defconfig
@@ -17,6 +17,7 @@
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_MISC_INIT_R=y
 CONFIG_SYS_PROMPT="dragonboard820c => "
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_MD5SUM=y
 CONFIG_CMD_MEMINFO=y
 CONFIG_CMD_GPIO=y