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/bcm968580xref_ram_defconfig b/configs/bcm968580xref_ram_defconfig
index d1a17c7..feda8f4 100644
--- a/configs/bcm968580xref_ram_defconfig
+++ b/configs/bcm968580xref_ram_defconfig
@@ -18,6 +18,7 @@
 CONFIG_SUPPORT_RAW_INITRD=y
 CONFIG_DISPLAY_BOARDINFO_LATE=y
 CONFIG_HUSH_PARSER=y
+CONFIG_SYS_MAXARGS=24
 CONFIG_CMD_GPIO=y
 CONFIG_CMD_MTD=y
 CONFIG_CMD_NAND=y