i965/blorp: Get rid of redundant num_samples blorp param.

i965/blorp: Get rid of redundant num_samples blorp param.

Previously, brw_blorp_params contained two fields for determining
sample count: num_samples (which determined the multisample
configuration of the rendering pipeline) and dst.num_samples (which
determined the multisample configuration of the render target
surface).  This was redundant, since both fields had to be set to the
same value to avoid rendering errors.

This patch eliminates num_samples to avoid future confusion.

Reviewed-by: Chad Versace <chad.versace@linux.intel.com>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>