ARM: dts: rmobile: Factor out U-Boot extras

Pull out u-boot extras into dtsi files to make synchronization of DTS
from Linux kernel as easy as a simple copy. All the U-Boot extras are
now in *-u-boot.dts* files instead.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/configs/r8a7796_salvator-x_defconfig b/configs/r8a7796_salvator-x_defconfig
index 9055c29..cf0b31a 100644
--- a/configs/r8a7796_salvator-x_defconfig
+++ b/configs/r8a7796_salvator-x_defconfig
@@ -4,7 +4,7 @@
 CONFIG_RCAR_GEN3=y
 CONFIG_R8A7796=y
 CONFIG_TARGET_SALVATOR_X=y
-CONFIG_DEFAULT_DEVICE_TREE="r8a7796-salvator-x"
+CONFIG_DEFAULT_DEVICE_TREE="r8a7796-salvator-x-u-boot"
 CONFIG_SMBIOS_PRODUCT_NAME=""
 # CONFIG_ARCH_FIXUP_FDT_MEMORY is not set
 CONFIG_USE_BOOTARGS=y