[SCSI] qla2xxx: Remove two superfluous tests.

Since ha->model_desc is an array comparing it against NULL is
superfluous. Hence remove these tests.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Saurav Kashyap <saurav.kashyap@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>