[SCSI] hpsa: refactor hpsa_figure_bus_target_lun

It should call hpsa_set_bus_target_lun rather
than individually setting bus, target and lun.

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>