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/k2g_evm_defconfig b/configs/k2g_evm_defconfig
index db21695..fc33225 100644
--- a/configs/k2g_evm_defconfig
+++ b/configs/k2g_evm_defconfig
@@ -33,6 +33,7 @@
 CONFIG_SPL_POWER=y
 CONFIG_SPL_SPI_LOAD=y
 CONFIG_SYS_SPI_U_BOOT_OFFS=0x10000
+CONFIG_SYS_MAXARGS=64
 CONFIG_SYS_I2C_EEPROM_ADDR_LEN=2
 CONFIG_SYS_EEPROM_PAGE_WRITE_BITS=6
 CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS=20