nfp: store NSP ABI version in state structure

We read the status register on each NSP open, we can store the NSP
ABI version in the state structure so that we don't have to read
it again.

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