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/m53evk_defconfig b/configs/m53evk_defconfig
index 061c588..7216774 100644
--- a/configs/m53evk_defconfig
+++ b/configs/m53evk_defconfig
@@ -12,6 +12,8 @@
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/aries/m53evk/imximage.cfg"
 CONFIG_ENV_IS_IN_NAND=y
 CONFIG_BOOTDELAY=3
+CONFIG_USE_BOOTARGS=y
+CONFIG_BOOTARGS="console=ttymxc1,115200"
 # CONFIG_CONSOLE_MUX is not set
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 CONFIG_VERSION_VARIABLE=y