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/socfpga_agilex_defconfig b/configs/socfpga_agilex_defconfig
index bfbbd9b..c8ccb05 100644
--- a/configs/socfpga_agilex_defconfig
+++ b/configs/socfpga_agilex_defconfig
@@ -27,6 +27,7 @@
 CONFIG_SYS_SPI_U_BOOT_OFFS=0x3c00000
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="SOCFPGA_AGILEX # "
+CONFIG_SYS_MAXARGS=64
 CONFIG_CMD_MEMTEST=y
 CONFIG_CMD_GPIO=y
 CONFIG_CMD_I2C=y