nfp: separate data path information from the reset of adapter structure

Move all data path information into a separate structure.  This way
we will be able to allocate new data path with all new rings etc.
and swap it in easily.

No functional changes.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>