nfp: nsp: allow the use of DMA buffer

Newer versions of NSP can access host memory.  Simplest access
type requires all data to be in one contiguous area.  Since we
don't have the guarantee on where callers of the NSP ABI will
allocate their buffers we allocate a bounce buffer and copy
the data in and out.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>