nfp: make bar_lock a semaphore

We will need to release the bar lock from a workqueue
so move from a mutex to a semaphore.  This lock should
not be too hot.  Unfortunately semaphores don't have
lockdep support.

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>