ibm_rtl: Loosen the DMI criteria to all IBM machines

Allow all IBM machines to pass the DMI check so that we
don't have to add them one by one to the driver.  Any IBM
machine that has the _RTL_ table in the EBDA will work.

Signed-off-by: Vernon Mauery <vernux@us.ibm.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>