staging: vboxvideo: Drop duplicate vbox_err.h file

Switch to the more complete vbox_err.h file from include/linux which got
added with the merging of the vboxguest driver.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>