[SCSI] qla2xxx: Drop srb reference before waiting for completion.

This patch fixes a regression introduced by commit
083a469db4ecf3b286a96b5b722c37fc1affe0be

qla2xxx_eh_wait_on_command() is waiting for an srb to
complete, which will never happen as the routine took
a reference to the srb previously and will only drop it
after this function. So every command abort will fail.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: Madhuranath Iyengar <Madhu.Iyengar@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>