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/mx6sabreauto_defconfig b/configs/mx6sabreauto_defconfig
index 053026d..f5097c9 100644
--- a/configs/mx6sabreauto_defconfig
+++ b/configs/mx6sabreauto_defconfig
@@ -41,6 +41,7 @@
 CONFIG_SPL_USB_SDP_SUPPORT=y
 CONFIG_SPL_WATCHDOG=y
 CONFIG_HUSH_PARSER=y
+CONFIG_SYS_MAXARGS=32
 CONFIG_CMD_BOOTZ=y
 CONFIG_CMD_DFU=y
 # CONFIG_CMD_FLASH is not set