nv50: allow forcing PMPEG use, for ease of testing

This also allows people who don't want to install the binary blobs
required for VP2 to still get MPEG decoding.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>

src/gallium/drivers/nv50/nv50_context.c

@@ -258,7 +258,8 @@ nv50_create(struct pipe_screen *pscreen, void *priv)
    draw_set_rasterize_stage(nv50->draw, nv50_draw_render_stage(nv50));
 #endif
 
-   if (screen->base.device->chipset < 0x84) {
+   if (screen->base.device->chipset < 0x84 ||
+       debug_get_bool_option("NOUVEAU_PMPEG", FALSE)) {
       /* PMPEG */
       nouveau_context_init_vdec(&nv50->base);
    } else if (screen->base.device->chipset < 0x98 ||

src/gallium/drivers/nv50/nv50_screen.c

@@ -647,7 +647,8 @@ nv50_screen_create(struct nouveau_device *dev)
 
    nv50_screen_init_resource_functions(pscreen);
 
-   if (screen->base.device->chipset < 0x84) {
+   if (screen->base.device->chipset < 0x84 ||
+       debug_get_bool_option("NOUVEAU_PMPEG", FALSE)) {
       /* PMPEG */
       nouveau_screen_init_vdec(&screen->base);
    } else if (screen->base.device->chipset < 0x98 ||