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/igep00x0_defconfig b/configs/igep00x0_defconfig
index f0d6ac5..24d6502 100644
--- a/configs/igep00x0_defconfig
+++ b/configs/igep00x0_defconfig
@@ -38,6 +38,7 @@
 CONFIG_SPL_OS_BOOT=y
 CONFIG_SPL_FALCON_BOOT_MMCSD=y
 CONFIG_SYS_MMCSD_RAW_MODE_KERNEL_SECTOR=0x1700
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_SPL=y
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_NAND=y