egl: remove Options::Platform handling

The full set of attributes is already handled with previous patches.
Thus all this is not dead code.

v2 (Emil) - split from a larger patch.

Reviewed-by: Mathias Fröhlich <Mathias.Froehlich@web.de>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Marek Olšák <marek.olsak@amd.com>

src/egl/main/egldisplay.h

@@ -167,7 +167,6 @@ struct _egl_display
    /* options that affect how the driver initializes the display */
    struct {
       EGLBoolean ForceSoftware; /**< Use software path only */
-      void *Platform;         /**< Platform-specific options */
       EGLAttrib *Attribs;     /**< Platform-specific options */
    } Options;