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/include/config_fsl_chain_trust.h b/include/config_fsl_chain_trust.h
index 6ec577b..4bbcd13 100644
--- a/include/config_fsl_chain_trust.h
+++ b/include/config_fsl_chain_trust.h
@@ -28,7 +28,7 @@
  *	 "41066b564c6ffcef40ccbc1e0a5d0d519604000c785d97bbefd25e4d288d1c8b"
  */
 
-#ifdef CONFIG_BOOTARGS
+#ifdef CONFIG_USE_BOOTARGS
 #define CONFIG_SET_BOOTARGS	"setenv bootargs \'" CONFIG_BOOTARGS" \';"
 #else
 #define CONFIG_SET_BOOTARGS	"setenv bootargs \'root=/dev/ram "	\