softpipe: Also mark textures as dirty when updating the framebuffer state

softpipe: Also mark textures as dirty when updating the framebuffer state

At this point all the draw caches are flushed to the old attached textures,
so the read caches of these textures will need to be updated too.

Fixes:
   dEQP-GLES3.functional.fbo.color.repeated_clear.sample.tex2d.*

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>