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/r8a77970_eagle_defconfig b/configs/r8a77970_eagle_defconfig
index 7b050d8..b6a113a 100644
--- a/configs/r8a77970_eagle_defconfig
+++ b/configs/r8a77970_eagle_defconfig
@@ -22,6 +22,7 @@
 CONFIG_BOOTCOMMAND="tftp 0x48080000 Image; tftp 0x48000000 Image-r8a77970-eagle.dtb; booti 0x48080000 - 0x48000000"
 CONFIG_DEFAULT_FDT_FILE="r8a77970-eagle.dtb"
 CONFIG_HUSH_PARSER=y
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_BOOTZ=y
 CONFIG_CMD_DFU=y
 CONFIG_CMD_GPIO=y