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/xilinx_zynqmp_virt_defconfig b/configs/xilinx_zynqmp_virt_defconfig
index 3589407..8b1529d 100644
--- a/configs/xilinx_zynqmp_virt_defconfig
+++ b/configs/xilinx_zynqmp_virt_defconfig
@@ -40,6 +40,7 @@
 CONFIG_SYS_SPI_U_BOOT_OFFS=0x100000
 CONFIG_SPL_ATF=y
 CONFIG_SPL_ATF_NO_PLATFORM_PARAM=y
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_BOOTMENU=y
 CONFIG_CMD_THOR_DOWNLOAD=y
 CONFIG_CMD_NVEDIT_EFI=y