driconf: add force_integer_tex_nearest option

And enable it for "GRID Autosport" and "DIRT: Showdown" games.

CC: 20.1 <mesa-stable@lists.freedesktop.org>
Closes: https://gitlab.freedesktop.org/mesa/mesa/issues/1258
Reviewed-by: Timothy Arceri <tarceri@itsqueeze.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4647>

src/mesa/state_tracker/st_extensions.c

@@ -1205,6 +1205,8 @@ void st_init_extensions(struct pipe_screen *screen,
 
    consts->GLSLZeroInit = options->glsl_zero_init;
 
+   consts->ForceIntegerTexNearest = options->force_integer_tex_nearest;
+
    consts->VendorOverride = options->force_gl_vendor;
 
    consts->UniformBooleanTrue = consts->NativeIntegers ? ~0U : fui(1.0f);