gallium/util: replace pipe_thread_wait() with thrd_join()

gallium/util: replace pipe_thread_wait() with thrd_join()

Replace done using:
find ./src -type f -exec sed -i -- \
's:pipe_thread_wait(\([^)]*\)):thrd_join(\1, NULL):g' {} \;

Reviewed-by: Plamena Manolova <plamena.manolova@intel.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>