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/sama5d2_ptc_spiflash_defconfig b/configs/sama5d2_ptc_spiflash_defconfig
index 419f29b..9ec10b9 100644
--- a/configs/sama5d2_ptc_spiflash_defconfig
+++ b/configs/sama5d2_ptc_spiflash_defconfig
@@ -10,6 +10,8 @@
 CONFIG_SYS_EXTRA_OPTIONS="SAMA5D2,SYS_USE_SERIALFLASH"
 CONFIG_ENV_IS_IN_SPI_FLASH=y
 CONFIG_BOOTDELAY=3
+CONFIG_USE_BOOTARGS=y
+CONFIG_BOOTARGS="console=ttyS0,57600 earlyprintk mtdparts=atmel_nand:6M(bootstrap)ro, 6M(kernel)ro,-(rootfs) rootfstype=ubifs ubi.mtd=2 root=ubi0:rootfs"
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_SPL=y
 # CONFIG_CMD_IMI is not set