The previous implementation will just skip the rendering
which is not good.
Signed-off-by: Zhigang Gong <zhigang.gong@linux.intel.com>

Due to the coordinate system on EGL is different from FBO
object. To support EGL surface well, we add this new feature.
When calling glamor_init from EGL ddx driver, it should use
the new flag GLAMOR_INVERTED_Y_AXIS.

It's not an offset from pixmap coords to composited pixmap coords,
it's an offset from screen-relative window drawable coords to
composited pixmap coords.