This way the mappings can be modified for any vm area, not only the
process that is running.
Why? This allows mapping pages to kernel dynamically, this functionality
will be presented later.
The task_group specific list can be used to store information about
mmappings.
For a driver or filesystem performing mmap can also enable munmap by
adding an item to this list using mm_map_add(). The item is then
returned in the corresponding munmap call.
Signed-off-by: Jukka Laitinen <jukkax@ssrc.tii.ae>