tgsi: Mark the tgsi_exec_channel and tgsi_double_channel ALIGN16.

We allocate them all align16, so mark the unions (and their container
structs) that way so the compiler can do aligned SSE load/stores.

glmark2 -b loop FPS +0.197265% +/- 0.117633% (n=1906)

Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10604>
2 files changed