nvk: Fix geometry shader active stream mask

nvk: Fix geometry shader active stream mask

This sets StreamOutMask in the shader header correctly based on:
https://download.nvidia.com/open-gpu-doc/Shader-Program-Header/1/Shader-Program-Header.html

After this fix transform feedback CTS tests with geometry shader streams
are passing.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24326>