In case of UEFI, RSDP doesn't have to be located in lowmem,
it could be placed at any address. Make sure that test won't
break if it is placed above the first 4Gb of address space.

PS:
While at it cleanup some local variables as we don't really
need them.
Signed-off-by: NIgor Mammedov <imammedo@redhat.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <1556808723-226478-5-git-send-email-imammedo@redhat.com>
Reviewed-by: NWei Yang <richardw.yang@linux.intel.com>
Tested-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>