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/rzg2_beacon_defconfig b/configs/rzg2_beacon_defconfig
index 6c8a94a..608be08 100644
--- a/configs/rzg2_beacon_defconfig
+++ b/configs/rzg2_beacon_defconfig
@@ -20,6 +20,7 @@
 CONFIG_DEFAULT_FDT_FILE="r8a774a1-beacon-rzg2m-kit.dtb"
 # CONFIG_BOARD_EARLY_INIT_F is not set
 CONFIG_HUSH_PARSER=y
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_BOOTZ=y
 CONFIG_CMD_GPIO=y
 CONFIG_CMD_I2C=y