Add nvme initiator devloss support

The existing implementation was based on no devloss behavior in the
transport (e.g. immediate teardown) so code didn't properly handle
delayed nvme rport device unregister calls.  In addition, the driver was
not correctly cycling the rport port role for each
register-unregister-reregister process.

This patch does the following:

Rework the code to properly handle rport device unregister calls and
potential re-allocation of the remoteport structure if the port comes
back in under dev_loss_tmo.

Correct code that was incorrectly cycling the rport port role for each
register-unregister-reregister process.

Prep the code to enable calling the nvme_fc transport api to dynamically
update dev_loss_tmo when the scsi sysfs interface changes it.

Memset the rpinfo structure in the registration call to enforce "accept
nvme transport defaults" in the registration call.  Driver parameters do
influence the dev_loss_tmo transport setting dynamically.

Simplifies the register function: the driver was incorrectly searching
its local rport list to determine resume or new semantics, which is not
valid as the transport already handles this.  The rport was resumed if
the rport handed back matches the ndlp->nrport pointer.  Otherwise,
devloss fired and the ndlp's nrport is NULL.
Signed-off-by: NDick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: NJames Smart <james.smart@broadcom.com>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>