Convert CONFIG_SYS_BARGSIZE to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_BARGSIZE

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/stmark2_defconfig b/configs/stmark2_defconfig
index 64ac661..e56ca93 100644
--- a/configs/stmark2_defconfig
+++ b/configs/stmark2_defconfig
@@ -8,6 +8,7 @@
 CONFIG_SYS_LOAD_ADDR=0x40010000
 CONFIG_TARGET_STMARK2=y
 CONFIG_MCFTMR=y
+CONFIG_SYS_BARGSIZE=256
 CONFIG_TIMESTAMP=y
 CONFIG_SYS_MONITOR_BASE=0x47E00400
 CONFIG_USE_BOOTARGS=y