net/pkt: Add new allocators

These struct net_pkt allocators will give the possibility to allocate at
once the net_pkt and the buffer associated with, taking care of the
header space and MTU relevantly.

This enables to use the variable length allocator from net_buf. However,
it is not yet the default and is set as experimental.

As it is provided in parallel to existing allocators, it has to keep a
slab per-direction and thus a pointer in net_pkt, as well as appdata,
appdatalen etc... Resulting in "bloating" net_pkt. This will be solved
when, finally, former allocators will be removed.

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>
3 files changed