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/socfpga_is1_defconfig b/configs/socfpga_is1_defconfig
index 7d3e653..f90352f 100644
--- a/configs/socfpga_is1_defconfig
+++ b/configs/socfpga_is1_defconfig
@@ -6,6 +6,8 @@
 CONFIG_DEFAULT_DEVICE_TREE="socfpga_cyclone5_is1"
 CONFIG_FIT=y
 CONFIG_ENV_IS_IN_SPI_FLASH=y
+CONFIG_USE_BOOTARGS=y
+CONFIG_BOOTARGS="console=ttyS0,115200"
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE=y
 CONFIG_SYS_CONSOLE_ENV_OVERWRITE=y