modprobe: rework module removal without tree traversing

modprobe: rework module removal without tree traversing

Just like the module insertion, module removal is remade.

The dependencies line that comes from modules.dep already contains all
the dependencies necessary to remove that module. Therefore modprobe
doesn't have to do the recursion between the modules in order to remove
it. All we have to do is to remove in order:

For the module being removed:
----------------------------

1. softdeps (in reverse order)
2. deps (in reverse order)
3. module
4. postdeps (in reverse order)

For any of the dependencies:
----------------------------

1. softdeps (in reverse order)
2. module
3. softdeps (in reverse order)