[SCSI] fnic: prep for fc host dev loss tmo support

This removes the driver's get_host_def_dev_loss_tmo
callback and just has the driver set the dev loss
using the fc class fc_host_dev_loss_tmo macro like is
done for other fc params.

This also adds a set rport dev loss function so the
fc class host dev loss tmp sysfs support being added
in the fc class patch can update rports.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>