aco: disable sdwa on gfx11

Instead of SDWA v_mov_b32/v_xor_b32, we can use a combination of
v_add_u16/v_sub_u16 (add/sub swap, similar to xor swap) and v_perm_b32
with a literal.

I don't know yet if GFX11 adds any new instructions which makes this
easier, but this approach should have full functionality.

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16595>

src/amd/compiler/aco_assembler.cpp

@@ -705,6 +705,7 @@ emit_instruction(asm_context& ctx, std::vector<uint32_t>& out, Instruction* inst
          out.push_back(encoding);
          return;
       } else if (instr->isSDWA()) {
+         assert(ctx.gfx_level >= GFX8 && ctx.gfx_level < GFX11);
          SDWA_instruction& sdwa = instr->sdwa();
 
          /* first emit the instruction without the SDWA operand */