[SCSI] tmscsim: clean-up status codes

Remove redundant defines from the header, replace all occurances in the
code with standard SAM_STAT_ macros. Also fix what seems to be a typo in
testing for (status == H_OVER_UNDER_RUN)...

Signed-off-by: G. Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>