USB: usbtmc: fix big-endian probe of Rigol devices

Fix probe of Rigol devices on big-endian machines. A quirk for these
devices was introduced by commit c2e31483

 ("USB: usbtmc: Set
rigol_quirk if device is listed") but was only enabled on little-endian
machines.

Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>