gallium: Reinstate unconditional flushes.

Lost in commit e50dd26ca6.

Signed-off-by: Thomas Hellstrom <thellstrom-at-vmware-dot-com>

src/mesa/state_tracker/st_cb_drawpixels.c

@@ -906,6 +906,8 @@ st_CopyPixels(GLcontext *ctx, GLint srcx, GLint srcy,
    GLfloat *color;
    enum pipe_format srcFormat, texFormat;
 
+   pipe->flush(pipe, PIPE_FLUSH_RENDER_CACHE, NULL);
+
    st_validate_state(st);
 
    if (type == GL_STENCIL) {

src/mesa/state_tracker/st_cb_readpixels.c

@@ -357,6 +357,8 @@ st_readpixels(GLcontext *ctx, GLint x, GLint y, GLsizei width, GLsizei height,
    if (!dest)
       return;
 
+   st_flush(ctx->st, PIPE_FLUSH_RENDER_CACHE, NULL);
+
    if (format == GL_STENCIL_INDEX ||
        format == GL_DEPTH_STENCIL) {
       st_read_stencil_pixels(ctx, x, y, width, height,