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/work_92105_defconfig b/configs/work_92105_defconfig
index b8ded52..9e85d5c 100644
--- a/configs/work_92105_defconfig
+++ b/configs/work_92105_defconfig
@@ -8,6 +8,8 @@
 CONFIG_ENV_IS_IN_NAND=y
 CONFIG_CMD_MAX6957=y
 CONFIG_BOOTDELAY=3
+CONFIG_USE_BOOTARGS=y
+CONFIG_BOOTARGS="console=ttyS2,115200n8"
 CONFIG_VERSION_VARIABLE=y
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_BOARD_EARLY_INIT_F=y