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/imx6q_logic_defconfig b/configs/imx6q_logic_defconfig
index 560733e..ae454af 100644
--- a/configs/imx6q_logic_defconfig
+++ b/configs/imx6q_logic_defconfig
@@ -39,6 +39,7 @@
 CONFIG_SPL_USB_SDP_SUPPORT=y
 CONFIG_SPL_WATCHDOG=y
 CONFIG_SYS_PROMPT="i.MX6 Logic # "
+CONFIG_SYS_MAXARGS=32
 CONFIG_CMD_SPL=y
 CONFIG_CMD_SPL_NAND_OFS=0x1500000
 CONFIG_CMD_SPL_WRITE_SIZE=0x00100000