[SCSI] libfc: rearrange code in fc_rport_work

This is a cleanup without semantic changes to use a switch
statement instead of a series of if-statements in fc_rport_work(),
and to move some declarations up to the top.

Signed-off-by: Joe Eykholt <jeykholt@cisco.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>