image_types.bbclass: add dependency do_image_wic -> do_bootimg

image_types.bbclass: add dependency do_image_wic -> do_bootimg

To produce certain types of images wic uses do_bootimg results
to assemble final image. For example, it copies BOOT/EFI directory
produced by do_bootimg to boot partition for every EFI image.

The tricky part of this is that do_bootimg task is not always run,
so we can't always make do_image_wic depend on do_bootimg. We only
need to do it if do_bootimg present in task graph.

Thank to Cristopher Larson for this fix.

(From OE-Core rev: 1a961b4becf677c9eb07c5b24a8ddb75044663d1)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>