st/mesa: use PIPE_BIND_DISPLAY_TARGET when checking for sRGB capability

When we're checking if the framebuffer is sRGB capable, call
is_format_supported() with the PIPE_BIND_DISPLAY_TARGET flag.

Reviewed-by: Charmaine Lee <charmainel@vmware.com>

src/mesa/state_tracker/st_manager.c

@@ -452,7 +452,8 @@ st_framebuffer_create(struct st_context *st,
           st_pipe_format_to_mesa_format(srgb_format) != MESA_FORMAT_NONE &&
           screen->is_format_supported(screen, srgb_format,
                                       PIPE_TEXTURE_2D, stfbi->visual->samples,
-                                      PIPE_BIND_RENDER_TARGET))
+                                      (PIPE_BIND_DISPLAY_TARGET |
+                                       PIPE_BIND_RENDER_TARGET)))
          mode.sRGBCapable = GL_TRUE;
    }