[RFC PATCH 10/13] switchtec_ntb: implement doorbell registers

Pretty straightforward implementation of doorbell registers. The shift and mask were setup in an earlier patch and this just hooks up the approprirate portion of the idb register as the local doorbells and the opposite portion of odb as the peer doorbells. The db mask is protected by a spinlock to

[RFC PATCH 10/13] switchtec_ntb: implement doorbell registers

Pretty straightforward implementation of doorbell registers. The shift and mask were setup in an earlier patch and this just hooks up the approprirate portion of the idb register as the local doorbells and the opposite portion of odb as the peer doorbells. The db mask is protected by a spinlock to