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/at91sam9rlek_mmc_defconfig b/configs/at91sam9rlek_mmc_defconfig
index 29ede1c..807c980 100644
--- a/configs/at91sam9rlek_mmc_defconfig
+++ b/configs/at91sam9rlek_mmc_defconfig
@@ -7,6 +7,8 @@
 CONFIG_SYS_EXTRA_OPTIONS="AT91SAM9RL,SYS_USE_MMC"
 CONFIG_ENV_IS_IN_FAT=y
 CONFIG_BOOTDELAY=3
+CONFIG_USE_BOOTARGS=y
+CONFIG_BOOTARGS="console=ttyS0,115200 mtdparts=atmel_nand:8M(bootstrap/uboot/kernel)ro,-(rootfs) root=/dev/mmcblk0p2 rw rootwait"
 # CONFIG_CONSOLE_MUX is not set
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 # CONFIG_DISPLAY_BOARDINFO is not set