device_tree: s/qemu_devtree/qemu_fdt globally

The qemu_devtree API is a wrapper around the fdt_ set of APIs.
Rename accordingly.

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
[agraf: also convert hw/arm/virt.c]
Signed-off-by: Alexander Graf <agraf@suse.de>
device_tree: qemu_fdt_setprop: Rename val_array arg

Looking at the implementation, this doesn't really have a lot to do
with arrays. Its just a pointer to a buffer and is passed through
to the wrapped fn (qemu_fdt_setprop) unchanged. So rename to make it
consistent with libfdt, which in the wrapped function just calls it
"val".

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: Alexander Graf <agraf@suse.de>