NTB: Correct USD/DSD Identification

commit b6750cfe upstream.

Due to ambiguous documentation, the USD/DSD identification is backward
when compared to the setting in BIOS.  Correct the bits to match the
BIOS setting.

Signed-off-by: Jon Mason <jon.mason@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>