sdcard_image-sunxi.bbclass: fix copying device tree files not working
sdcard_image-sunxi.bbclass: fix copying device tree files not working

The image class assumes the working directory is the directory
containg the kernel and device tree files but this isn't always the
case.

Signed-off-by: Jonathan Liu <44960b6aa03eb2fb89c62409a43f0b56d13ff84f@gmail.com>

ebutera/meta-sunxi,soderstrom-rikard/meta-sunxi,ebutera/meta-sunxi,net147/meta-sunxi,linux-sunxi/meta-sunxi,net147/meta-sunxi,soderstrom-rikard/meta-sunxi,geomatsi/meta-sunxi,twoerner/meta-sunxi,twoerner/meta-sunxi,linux-sunxi/meta-sunxi,geomatsi/meta-sunxi,linux-sunxi/meta-sunxi