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/MPC8349ITXGP_defconfig b/configs/MPC8349ITXGP_defconfig
index df421ad..3b90e15 100644
--- a/configs/MPC8349ITXGP_defconfig
+++ b/configs/MPC8349ITXGP_defconfig
@@ -5,6 +5,8 @@
 CONFIG_OF_STDOUT_VIA_ALIAS=y
 CONFIG_SYS_EXTRA_OPTIONS="MPC8349ITXGP,SYS_TEXT_BASE=0xFE000000"
 CONFIG_BOOTDELAY=6
+CONFIG_USE_BOOTARGS=y
+CONFIG_BOOTARGS="root=/dev/nfs rw nfsroot=:/nfsroot/rootfs ip=::::mpc8349emitxgp:eth0:off console=ttyS0,115200"
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="MPC8349E-mITX-GP> "
 CONFIG_CMD_I2C=y