During access_ok checks, addr increases as we iterate over the data
structure, thus addr + len - 1 will point beyond the end of region we
are translating.  Harmless since we then verify that the region covers
addr, but let's not waste cpu cycles.
Reported-by: NKoichiro Den <den@klaipeden.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
Acked-by: NKoichiro Den <den@klaipeden.com>