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/am335x_baltos_defconfig b/configs/am335x_baltos_defconfig
index 5ad078f..653761b 100644
--- a/configs/am335x_baltos_defconfig
+++ b/configs/am335x_baltos_defconfig
@@ -26,6 +26,7 @@
 CONFIG_SPL_POWER=y
 CONFIG_SPL_WATCHDOG=y
 CONFIG_SPL_YMODEM_SUPPORT=y
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_ASKENV=y
 CONFIG_CMD_EEPROM=y
 CONFIG_SYS_I2C_EEPROM_ADDR_LEN=2