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/hikey_defconfig b/configs/hikey_defconfig
index 6f33bba..379dd84 100644
--- a/configs/hikey_defconfig
+++ b/configs/hikey_defconfig
@@ -17,6 +17,7 @@
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_MISC_INIT_R=y
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_GPIO=y
 CONFIG_CMD_MMC=y
 CONFIG_CMD_USB=y