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/brppt1_mmc_defconfig b/configs/brppt1_mmc_defconfig
index f1e7f81..2a7ddb4 100644
--- a/configs/brppt1_mmc_defconfig
+++ b/configs/brppt1_mmc_defconfig
@@ -38,6 +38,7 @@
 CONFIG_SPL_WATCHDOG=y
 CONFIG_SPL_YMODEM_SUPPORT=y
 CONFIG_HUSH_PARSER=y
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_IMI is not set
 # CONFIG_CMD_XIMG is not set