[SCSI] qla2xxx: Fix array subscript is above array bounds in qla2xx_build_scsi_type_6...

The additional increment of dsd_seg was causing the compiler to throw an array
out of bounds warning. This patch moves to a direct assignment of
cmd_pkt->fcp_data_dseg_len so that the compiler doesn't generate an array out
bounds warning.

Signed-off-by: Chad Dupuis <chad.dupuis@qlogic.com>
Signed-off-by: Madhuranath Iyengar <Madhu.Iyengar@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>