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/ls2080aqds_sdcard_defconfig b/configs/ls2080aqds_sdcard_defconfig
index 843c1e7..084b2b9 100644
--- a/configs/ls2080aqds_sdcard_defconfig
+++ b/configs/ls2080aqds_sdcard_defconfig
@@ -37,6 +37,7 @@
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_SPL_I2C=y
 CONFIG_SPL_MPC8XXX_INIT_DDR=y
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_GREPENV=y
 CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS=5
 CONFIG_CMD_I2C=y