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/cl-som-imx7_defconfig b/configs/cl-som-imx7_defconfig
index 7c70825..8c98762 100644
--- a/configs/cl-som-imx7_defconfig
+++ b/configs/cl-som-imx7_defconfig
@@ -31,6 +31,7 @@
 CONFIG_SPL_SPI_LOAD=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="CL-SOM-iMX7 # "
+CONFIG_SYS_MAXARGS=32
 CONFIG_CMD_BOOTZ=y
 # CONFIG_BOOTM_NETBSD is not set
 # CONFIG_BOOTM_PLAN9 is not set