sunxi: dts: Add a CONFIG_DEFAULT_DEVICE_TREE setting to all sunxi boards

This is a preparation patch for switching all sunxi boards over to using
the driver model.

Note that rather then defining both CONFIG_DEFAULT_DEVICE_TREE (for u-boot)
and CONFIG_FDTFILE (for the kernel), this commit simply replaces all
CONFIG_FDTFILE defconfig settings with CONFIG_DEFAULT_DEVICE_TREE and
uses CONFIG_DEFAULT_DEVICE_TREE for setting the default fdtfile env value
in sunxi-common.h .

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
diff --git a/configs/r7-tv-dongle_defconfig b/configs/r7-tv-dongle_defconfig
index 563fa1a..d7ed165 100644
--- a/configs/r7-tv-dongle_defconfig
+++ b/configs/r7-tv-dongle_defconfig
@@ -1,6 +1,6 @@
 CONFIG_SPL=y
 CONFIG_SYS_EXTRA_OPTIONS="AXP152_POWER,USB_EHCI"
-CONFIG_FDTFILE="sun5i-a10s-r7-tv-dongle.dtb"
+CONFIG_DEFAULT_DEVICE_TREE="sun5i-a10s-r7-tv-dongle"
 CONFIG_USB1_VBUS_PIN="PG13"
 CONFIG_ARM=y
 CONFIG_ARCH_SUNXI=y