i965: Make a BRW_NEW_FAST_CLEAR_COLOR dirty bit.

i965: Make a BRW_NEW_FAST_CLEAR_COLOR dirty bit.

When changing fast clear colors, we need to emit new SURFACE_STATE
with the updated color at the next draw call.

Most things work today because the atoms that handle SURFACE_STATE
for images (mutable images, textures, render targets) also listen to
BRW_NEW_BLORP, causing us to re-emit these on every BLORP operation.
However, this is overkill - most BLORP operations don't require us
to re-emit SURFACE_STATE.

One case where this is broken today is a fast clear to a different
color followed by a non-coherent framebuffer fetch.  The renderbuffer
read atom doesn't listen to BRW_NEW_BLORP, and would not get the new
fast clear color.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>