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/sc_sps_1_defconfig b/configs/sc_sps_1_defconfig
index 44c5f51..a6a3c3b 100644
--- a/configs/sc_sps_1_defconfig
+++ b/configs/sc_sps_1_defconfig
@@ -6,6 +6,8 @@
 CONFIG_SPL_SERIAL_SUPPORT=y
 CONFIG_ENV_IS_IN_MMC=y
 CONFIG_BOOTDELAY=3
+CONFIG_USE_BOOTARGS=y
+CONFIG_BOOTARGS="console=ttyAMA0,115200"
 CONFIG_VERSION_VARIABLE=y
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_ARCH_MISC_INIT=y