i965: Update multisampling state for Broadwell.

i965: Update multisampling state for Broadwell.

On previous platforms, 3DSTATE_MULTISAMPLE contained the number of
samples, pixel location, and the positions of each sample within a pixel
for each multisampling mode (4x and 8x).  It was also a non-pipelined
command, presumably since changing the sample positions is fairly
drastic.

Broadwell improves upon this by splitting the sample positions out into
a separate non-pipelined state packet, 3DSTATE_SAMPLE_PATTERN.  With
that removed, 3DSTATE_MULTISAMPLE becomes a pipelined state packet.

Broadwell also supports 2x and 16x multisampling, in addition to the 4x
and 8x supported by Gen7.  This patch, however, does not implement 2x
and 16x.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Signed-off-by: Chad Versace <chad.versace@linux.intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>