ACPI: Remove Dell Optiplex GX240 from the ACPI blacklist

I have a Dell Optiplex GX240 and when I boot Linux, ACPI gets set up by only
acpi=ht.  dmesg shows the following line:

   DELL GX240 detected: force use of acpi=ht

Everything seemed to be fine.  However, I discovered that everything is not
fine.  The USB controller works so slowly that copying a few (uncached) 1
megabyte large photos from a USB-enabled digital camera takes many minutes
instead of a couple of seconds.

I am using Linux 2.6.21.1 on a Debian 4.0 ("Etch") system.

I thought that this might be related to ACPI.  So I tried to boot with _only_
"acpi=force" appended to the kernel command line.  Voila, the USB controller
started to work at full speed and copying photos from my digital camera took
only seconds.

I tested the system with "acpi=force" and could not find anything which did
not work.

I thought that this might be related to interrupts and APIC as well.  (Note
that this is APIC, not ACPI.) I tried booting with _only_ "noapic" and
"nolapic" appended to the command line.  Again, the USB controller started to
work at full speed.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>