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/imx8mm-cl-iot-gate_defconfig b/configs/imx8mm-cl-iot-gate_defconfig
index b418e86..adc653d 100644
--- a/configs/imx8mm-cl-iot-gate_defconfig
+++ b/configs/imx8mm-cl-iot-gate_defconfig
@@ -32,6 +32,7 @@
 CONFIG_SPL_POWER=y
 CONFIG_SPL_WATCHDOG=y
 CONFIG_SYS_PROMPT="u-boot=> "
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_BOOTEFI_SELFTEST=y
 CONFIG_CMD_NVEDIT_EFI=y
 CONFIG_CMD_EEPROM=y