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/r8a77990_ebisu_defconfig b/configs/r8a77990_ebisu_defconfig
index fba03a7..33995af 100644
--- a/configs/r8a77990_ebisu_defconfig
+++ b/configs/r8a77990_ebisu_defconfig
@@ -24,6 +24,7 @@
 # CONFIG_BOARD_EARLY_INIT_F is not set
 CONFIG_UPDATE_TFTP=y
 CONFIG_HUSH_PARSER=y
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_BOOTZ=y
 CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS=10
 CONFIG_CMD_DFU=y