softpipe: use pipe_get_tile_rgba_format()

Pass an explicit surface format as we do with pipe_put_tile_rgba_format().
This fixes the piglit fbo-srgb-blit test.  With GL_EXT_framebuffer_sRGB we
override the resource's format with an explicit format (linear vs. sRGB).
We need to do so both when getting and putting tiles.

Fixes https://bugs.freedesktop.org/show_bug.cgi?id=40402

Reviewed-by: Dave Airlie <airlied@redhat.com>

src/gallium/drivers/softpipe/sp_tile_cache.c

@@ -494,11 +494,12 @@ sp_find_cached_tile(struct softpipe_tile_cache *tc,
                               tile->data.depth32, 0/*STRIDE*/);
          }
          else {
-            pipe_get_tile_rgba(tc->pipe, pt,
-                               tc->tile_addrs[pos].bits.x * TILE_SIZE,
-                               tc->tile_addrs[pos].bits.y * TILE_SIZE,
-                               TILE_SIZE, TILE_SIZE,
-                               (float *) tile->data.color);
+            pipe_get_tile_rgba_format(tc->pipe, pt,
+                                      tc->tile_addrs[pos].bits.x * TILE_SIZE,
+                                      tc->tile_addrs[pos].bits.y * TILE_SIZE,
+                                      TILE_SIZE, TILE_SIZE,
+                                      tc->surface->format,
+                                      (float *) tile->data.color);
          }
       }
    }