Again, we'd like to keep the routines filling out the postfix together,
and this has a single remaining caller (once for vertex then immediately
for tiler).

By keeping them together we can avoid uploading the shared
memory/framebuffer structures twice in a row, saving a bit of memory in
the process.

We also fix a bug where bit 2 of gl_enables is incorrectly set on
Bifrost.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <mesa!6476>