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/db-88f6720_defconfig b/configs/db-88f6720_defconfig
index 8ebc781..f92f2c4 100644
--- a/configs/db-88f6720_defconfig
+++ b/configs/db-88f6720_defconfig
@@ -24,6 +24,7 @@
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_DISPLAY_BOARDINFO_LATE=y
 CONFIG_SPL_I2C=y
+CONFIG_SYS_MAXARGS=32
 CONFIG_CMD_I2C=y
 CONFIG_CMD_SPI=y
 CONFIG_CMD_USB=y