anv: Add pipeline_has_stage guards a few places

All of these worked before because they were depending on prog_data to be
null.  Soon, we won't be able to depend on a nice prog_data pointer and
it's nice to be more explicit anyway.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Cc: "12.0" <mesa-stable@lists.freedesktop.org>
(cherry picked from commit 13c09fdd0cfb62f3f45c39ad01a1c8f4b37c9c19)
4 files changed