egl: let each platform decided how to handle LIBGL_ALWAYS_SOFTWARE

My refactor in 47273d7312 missed this early return; because
of it, setting UseFallback one layer above actually prevented the
software path from being used.

Remove this early return and let each platform's dri2_initialize_*()
decide what it can do with the LIBGL_ALWAYS_SOFTWARE restriction.

platform_{surfaceless,x11,wayland} were already handling it themselves.

Fixes: 47273d7312 "egl: set UseFallback if LIBGL_ALWAYS_SOFTWARE is set"
Signed-off-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reported-by: Brendan King <Brendan.King@imgtec.com>

src/egl/drivers/dri2/egl_dri2.c

@@ -910,10 +910,6 @@ dri2_initialize(_EGLDriver *drv, _EGLDisplay *disp)
       return EGL_TRUE;
    }
 
-   /* not until swrast_dri is supported */
-   if (disp->Options.UseFallback)
-      return EGL_FALSE;
-
    switch (disp->Platform) {
    case _EGL_PLATFORM_SURFACELESS:
       ret = dri2_initialize_surfaceless(drv, disp);

src/egl/drivers/dri2/platform_android.c

@@ -1179,6 +1179,10 @@ dri2_initialize_android(_EGLDriver *drv, _EGLDisplay *dpy)
    const char *err;
    int ret;
 
+   /* Not supported yet */
+   if (disp->Options.UseFallback)
+      return EGL_FALSE;
+
    loader_set_logger(_eglLog);
 
    dri2_dpy = calloc(1, sizeof(*dri2_dpy));

src/egl/drivers/dri2/platform_drm.c

@@ -652,6 +652,10 @@ dri2_initialize_drm(_EGLDriver *drv, _EGLDisplay *disp)
    struct gbm_device *gbm;
    const char *err;
 
+   /* Not supported yet */
+   if (disp->Options.UseFallback)
+      return EGL_FALSE;
+
    loader_set_logger(_eglLog);
 
    dri2_dpy = calloc(1, sizeof *dri2_dpy);