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/uDPU_defconfig b/configs/uDPU_defconfig
index f7cd1a0..ed13a2b 100644
--- a/configs/uDPU_defconfig
+++ b/configs/uDPU_defconfig
@@ -24,6 +24,7 @@
 CONFIG_ARCH_EARLY_INIT_R=y
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_SYS_PROMPT="uDPU>> "
+CONFIG_SYS_MAXARGS=32
 # CONFIG_CMD_ELF is not set
 # CONFIG_CMD_IMI is not set
 # CONFIG_CMD_XIMG is not set