[SCSI] libfcoe: fix possible buffer overflow in fcoe_transport_show

possible buffer overflow in fcoe_transport_show when reaching the end of
buffer and crossing PAGE_SIZE boundary.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: Tomas Henzl <thenzl@redhat.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>