i965/urb: Allow blorp to record current settings

i965/urb: Allow blorp to record current settings

This makes it possible to skip urb re-configuration if the
subsequent renders agree with the settings.

Also allows blorp to allocate the maximun amount of vs entries
available. Core upload logic already knows how to calculate this.
Helps one synthetic benchmark.

Signed-off-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>