Allow qemu_devtree_setprop() to take arbitrary values

Allow qemu_devtree_setprop() to take arbitrary values

Currently qemu_devtree_setprop() expects the new property value to be
given as a uint32_t *.  While property values consisting of u32s are
common, in general they can have any bytestring value.

Therefore, this patch alters the function to take a void * instead,
allowing callers to easily give anything as the property value.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>