tgsi: set nonhelpermask for vertex shaders

tgsi: set nonhelpermask for vertex shaders

For atomic operations we really need to avoid executing unnecessary shaders, so for some
tests that just draw a single point we only want one vertex to get processed not 4,

this fixes a number of the atomic counters tests.

Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>