intel/compiler: store the FS inputs in WM prog data

intel/compiler: store the FS inputs in WM prog data

Store the fragment shader inputs in the program data so we can use them
later when required without needing the NIR shader.

Cc: mesa-stable@lists.freedesktop.org
Signed-off-by: Juan A. Suarez Romero <jasuarez@igalia.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Ivan Briano <ivan.briano@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/2010>