glx/dri2: don't return NULL in a function with no return.

Reported by gcc.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

glx/glxdri2.c

@@ -521,7 +521,7 @@ create_driver_context(__GLXDRIcontext * context,
                                           &major_ver, &minor_ver,
                                           &flags, &api, &reset,
                                           (unsigned *) error))
-                return NULL;
+                return;
 
             ctx_attribs[num_ctx_attribs++] = __DRI_CTX_ATTRIB_MAJOR_VERSION;
             ctx_attribs[num_ctx_attribs++] = major_ver;