[SCSI] fnic: fix for trusted cos

Modified fnic driver to let hardware insert the COS value. Set bit
in descriptor to 0 telling hardware to use its lif COS configurations
to insert the COS value in the frames.

Signed-off-by: Narsimhulu Musini <nmusini@cisco.com>
Signed-off-by: Hiral Patel <hiralpat@cisco.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>