Convert most remaining free-form fall-through comments to FALLTHROUGH

One exception is src/amd/addrlib/, for which -Wimplicit-fallthrough is
explicitly disabled.

Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Alyssa Rosenzweig <alyssa@collabora.com>
Reviewed-by: Juan A. Suarez <jasuarez@igalia.com>
Reviewed-by: Gert Wollny <gert.wollny@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10220>

src/compiler/glsl/glsl_to_nir.cpp

@@ -1543,7 +1543,7 @@ nir_visitor::visit(ir_call *ir)
       }
       case nir_intrinsic_vote_ieq:
          instr->num_components = 1;
-         /* fall-through */
+         FALLTHROUGH;
       case nir_intrinsic_vote_any:
       case nir_intrinsic_vote_all: {
          nir_ssa_dest_init(&instr->instr, &instr->dest, 1, 1, NULL);