[SCSI] bfa: change FC_ELS_TOV to 20sec

As per the FCP specs, the timeout for issuing ABTS is 20 sec; not 21
sec. Hence setting the TOV to 20 sec.

Signed-off-by: Vijaya Mohan Guvva <vmohan@brocade.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>