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/sei510_defconfig b/configs/sei510_defconfig
index e9f5781..c3572f9 100644
--- a/configs/sei510_defconfig
+++ b/configs/sei510_defconfig
@@ -24,6 +24,7 @@
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_MISC_INIT_R=y
 CONFIG_AVB_VERIFY=y
+CONFIG_SYS_MAXARGS=32
 # CONFIG_CMD_BDI is not set
 CONFIG_CMD_ADTIMG=y
 CONFIG_CMD_ABOOTIMG=y