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/dragonboard410c_defconfig b/configs/dragonboard410c_defconfig
index c78b4a6..0c8f030 100644
--- a/configs/dragonboard410c_defconfig
+++ b/configs/dragonboard410c_defconfig
@@ -4,6 +4,8 @@
 CONFIG_DEFAULT_DEVICE_TREE="dragonboard410c"
 CONFIG_DISTRO_DEFAULTS=y
 CONFIG_ENV_IS_NOWHERE=y
+CONFIG_USE_BOOTARGS=y
+CONFIG_BOOTARGS="console=ttyMSM0,115200n8"
 # CONFIG_DISPLAY_CPUINFO is not set
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_SYS_PROMPT="dragonboard410c => "