common: Move CONFIG_BOOTARGS to Kconfig

Also introduce CONFIG_USE_BOOTARGS option so we can control if
CONFIG_BOOTARGS defined at all.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
[trini: Resync r8a779[56]_ulcb, various ls10xx targets]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/nsim_700_defconfig b/configs/nsim_700_defconfig
index fabae32..59aabfb 100644
--- a/configs/nsim_700_defconfig
+++ b/configs/nsim_700_defconfig
@@ -5,6 +5,8 @@
 CONFIG_DEFAULT_DEVICE_TREE="nsim"
 CONFIG_ENV_IS_NOWHERE=y
 CONFIG_BOOTDELAY=3
+CONFIG_USE_BOOTARGS=y
+CONFIG_BOOTARGS="console=ttyARC0,115200n8"
 CONFIG_SYS_PROMPT="nsim# "
 # CONFIG_CMD_IMLS is not set
 # CONFIG_CMD_FLASH is not set