EGL: legacy-x11=dri2 should support hardware driver

Since MR !33891 EGL only supports a software driver (LLVM).
Routine dri3_x11_connect at
src/egl/drivers/dri2/platform_x11.c fails if DRI3 is not
available. So at that location variable *allow_dri2 should be set.

Looking at the major codition, we see it is not executed
if LIBGL_DRI3_DISABLE is set. In that case the hardware driver
is activated as desired. Previously this was not needed.
Also it is not practical, and not necessary.

I do not understand the major condition, so I did not change it.
This causes some duplicate coding.

Fixes: 323bad6b18 ("egl/x11: split out dri2 init entirely")
Signed-off-by: GKraats <vd.kraats@hccnet.nl>
Acked-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34530>
(cherry picked from commit 995dc61bf5)

.pick_status.json

@@ -1024,7 +1024,7 @@
         "description": "EGL: legacy-x11=dri2 should support hardware driver",
         "nominated": true,
         "nomination_type": 2,
-        "resolution": 0,
+        "resolution": 1,
         "main_sha": null,
         "because_sha": "323bad6b18717fcc395f67ef508e5a3d0aed7d02",
         "notes": null

src/egl/drivers/dri2/platform_x11.c

@@ -1989,8 +1989,15 @@ dri2_initialize_x11(_EGLDisplay *disp, bool *allow_dri2)
       /* the status here is ignored for zink-with-kopper and swrast,
        * otherwise return whatever error/fallback status as failure
        */
-      if (!dri2_dpy->kopper && !disp->Options.ForceSoftware && !status)
-         return EGL_FALSE;
+      if (!dri2_dpy->kopper && !disp->Options.ForceSoftware) {
+#ifdef HAVE_X11_DRI2
+         *allow_dri2 = !debug_get_bool_option("LIBGL_DRI2_DISABLE", false);
+#else
+         *allow_dri2 = false;
+#endif
+         if (!status)
+            return EGL_FALSE;
+      }
    }
 #endif
    if (!dri2_load_driver(disp))