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/ls1021atwr_sdcard_ifc_defconfig b/configs/ls1021atwr_sdcard_ifc_defconfig
index 73e5f5b..2d6b656 100644
--- a/configs/ls1021atwr_sdcard_ifc_defconfig
+++ b/configs/ls1021atwr_sdcard_ifc_defconfig
@@ -16,6 +16,8 @@
 CONFIG_SD_BOOT=y
 CONFIG_ENV_IS_IN_MMC=y
 CONFIG_BOOTDELAY=3
+CONFIG_USE_BOOTARGS=y
+CONFIG_BOOTARGS="console=ttyS0,115200 root=/dev/ram0"
 CONFIG_SILENT_CONSOLE=y
 # CONFIG_CONSOLE_MUX is not set
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y