kernel-module-split.bbclass: generate dependencies across recipes

kernel-module-split.bbclass: generate dependencies across recipes

The information retrieved via depmod is incomplete with
regards to kernel modules that are dependencies, in
particular where two kernel modules are built from
different source trees / recipes, which leads to incomplete
dependency information for packages created.

So far, our packages created didn't contain dependencies on
packages created by other recipes, as we solely use depmod
for that, and depmod can only work well after *all* kernel
modules have been copied into one place - it doesn't work
well in a staged approach.

Now that all .ko have correct dependency information at packaging
time, we can use that information to properly track dependencies
across recipies, and can combine the information from the
.modinfo elf section with the information from depmod.

Signed-off-by: André Draszik <git@andred.net>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>