nfp: replace spin_lock_bh with spin_lock in tasklet callback

As you are already in a tasklet, it is unnecessary to call spin_lock_bh.

Signed-off-by: jun qian <hangdianqj@163.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>