This fixes a *very* obscure bug, which only applies to VIA chipsets that
support UDMA-133 mode, and which is only known to be tickled by one
UDMA-66 hard drive (Maxtor 91360U4) that happens to report 80-wire cable
detection opposite to the ATA standard.

The bug appears in a test to see how the BIOS set up UDMA timing.  This
test is only reached when the drive says 80-wire *and* the chipset says
40-wire (which is only known to happen with this drive).

The timing bits that are checked represent clocks T minus 2, i.e., ((N -
2) * T).  But Vojtech forgot to subtract 2, and applied N = 8 rather
than N = 6 in the test.  Since the test masks the bits at 7, they are
always less than 8, and the test always succeeds, even though the BIOS
set UDMA-33.