i965: Print a total time for the different shader stages.

i965: Print a total time for the different shader stages.

Sometimes I've got a patch for a performance optimization that's not
showing a statistically significant performance difference on reported
FPS, but still seems like a good idea because it ought to reduce time
spent in the shader.  If I can see the total number of cycles spent in
the shader stage being optimized, it may show that the patch is still
worthwhile (or point out that it's actually broken in some way).