anv: report max dispatch width statistic

Most tools looking at shader stats assume that there is only a single resulting binary shader out of a single input. On Intel HW this is not always the case. So having a statistic on each variant that reports the maximum dispatch width helps showing improvement on a single shader in terms of how large we manage to compile it.

For shaders that can be compiled in multiple SIMD width (like fragment shaders), this will report the maximum dispatch width in the statistics of each variants.

Signed-off-by: Lionel Landwerlin lionel.g.landwerlin@intel.com