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/ten64_tfa_defconfig b/configs/ten64_tfa_defconfig
index 96bca83..77c8694 100644
--- a/configs/ten64_tfa_defconfig
+++ b/configs/ten64_tfa_defconfig
@@ -27,6 +27,7 @@
 # CONFIG_ID_EEPROM is not set
 CONFIG_PCI_INIT_R=y
 CONFIG_RESET_PHY_R=y
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_BOOTEFI_SELFTEST=y
 CONFIG_CMD_BOOTMENU=y
 CONFIG_CMD_GREPENV=y