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/giedi_defconfig b/configs/giedi_defconfig
index 4fbf7eb..0017a35 100644
--- a/configs/giedi_defconfig
+++ b/configs/giedi_defconfig
@@ -42,6 +42,7 @@
 CONFIG_SPL_WATCHDOG=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="U-Boot# "
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_CPU=y
 # CONFIG_BOOTM_NETBSD is not set
 # CONFIG_CMD_EXPORTENV is not set