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/lx2160ardb_tfa_stmm_defconfig b/configs/lx2160ardb_tfa_stmm_defconfig
index ce106fb..b1d8438 100644
--- a/configs/lx2160ardb_tfa_stmm_defconfig
+++ b/configs/lx2160ardb_tfa_stmm_defconfig
@@ -37,6 +37,7 @@
 CONFIG_BOOTARGS="console=ttyAMA0,115200 root=/dev/ram0 earlycon=pl011,mmio32,0x21c0000 ramdisk_size=0x2000000 default_hugepagesz=1024m hugepagesz=1024m hugepages=2 pci=pcie_bus_perf"
 CONFIG_MISC_INIT_R=y
 CONFIG_RESET_PHY_R=y
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_GREPENV=y
 CONFIG_CMD_NVEDIT_EFI=y
 CONFIG_CMD_EEPROM=y