ACPI: delete the "acpi=ht" boot option

acpi=ht was important in 2003 -- before ACPI was
universally deployed and enabled by default in
the major Linux distributions.

At that time, there were a fair number of people who
or chose to, or needed to, run with acpi=off,
yet also wanted access to Hyper-threading.

Today we find that many invocations of "acpi=ht"
are accidental, and thus is it possible that it
is doing more harm than good.

In 2.6.34, we warn on invocation of acpi=ht.
In 2.6.35, we delete the boot option.

Signed-off-by: Len Brown <len.brown@intel.com>