intel/compiler: make uses_pos_offset a tri-state

intel/compiler: make uses_pos_offset a tri-state

This value depends on the per-sample value which can be unknown at
compile time with graphics pipeline libraries. So we need to have this
dynamic has well and pick the right value when generating the
3DSTATE_PS/3DSTATE_WM packet.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Fixes: d8dfd153c5 ("intel/fs: Make per-sample and coarse dispatch tri-state")
Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22728>