[BUG] Intel xorg driver 2.20.2 overlay off-by-one bug

[Russell King - ARM Linux]

While reading through the Intel driver code, I spotted this in
I830SetPortAttributeOverlay:

        } else if (attribute == xvPipe) {
                xf86CrtcConfigPtr xf86_config = XF86_CRTC_CONFIG_PTR(scrn);
                if ((value < -1) || (value > xf86_config->num_crtc))
                        return BadValue;
                if (value < 0)
                        adaptor_priv->desired_crtc = NULL;
                else
                        adaptor_priv->desired_crtc = xf86_config->crtc[value];

This allows value == xf86_config->num_crtc to be valid, which would be
the CRTC number _after_ the last one in the array.  Presumably this is
not desired, and the test should be ">=".