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/bcm_ns3_defconfig b/configs/bcm_ns3_defconfig
index 9267bf3..a3ada3c 100644
--- a/configs/bcm_ns3_defconfig
+++ b/configs/bcm_ns3_defconfig
@@ -24,6 +24,7 @@
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="u-boot> "
+CONFIG_SYS_MAXARGS=64
 # CONFIG_SYS_XTRACE is not set
 CONFIG_CMD_GPT=y
 CONFIG_CMD_GPT_RENAME=y