342f3eac84 introduced a bug, 'base' is
incremented before use. The old code corrected this when unmapping, so
the new code should too.
Signed-off-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Keith Packard <keithp@keithp.com>