[SCSI] fc class: add fc host default default dev loss setting

This patch adds a fc_host setting to store the
default dev_loss_tmo. It is used if the driver
has a callack to get the value from the LLD. If
the callback is not set, then we use the fc class
module default value.

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