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/cortina_presidio-asic-pnand_defconfig b/configs/cortina_presidio-asic-pnand_defconfig
index 944fed6..996041a 100644
--- a/configs/cortina_presidio-asic-pnand_defconfig
+++ b/configs/cortina_presidio-asic-pnand_defconfig
@@ -20,6 +20,7 @@
 CONFIG_BOARD_EARLY_INIT_R=y
 CONFIG_LAST_STAGE_INIT=y
 CONFIG_SYS_PROMPT="G3#"
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_MTD=y
 CONFIG_CMD_WDT=y
 CONFIG_CMD_CACHE=y