As after we got a texture, no matter the texture is created
on the glamor_create_pixmap or on the egl layer, we all already
know the texture's width and height there. We don't need
to pass them in.
This commit also simply the glamor_egl_create_textured_screen to
reuse the egl_create_textured_pixmap. And also remove the useless
root image from the egl private structure. As now the root image
is bound to the screen image, we don't take care it separately
here. It will be freed at the screen closing.
Signed-off-by: Zhigang Gong <zhigang.gong@linux.intel.com>