shader: combine semantic name and index to bit value

With that we can correctly pass the bit that indicates invariant
in and outputs.

Also update the host_feature_check_version to enable
PIPE_CAP_TGSI_TEXTCOORD on the host in this case.

v2: Account for clients who don't have PIPE_CAP_TGSI_TEXCOORD enabled.

Part-of: <https://gitlab.freedesktop.org/virgl/virglrenderer/-/merge_requests/751>
3 files changed