gpu: honour DB_ALPHA_TO_MASK as alpha-to-coverage and keep its depth writes behind the shader

src/graphics/host_gpu/renderer/renderDraw.cpp

@@ -436,7 +436,7 @@ static bool DrawHasValidVertexShader(const HW::Shader& sh_ctx) {
 static bool PixelShaderHasDepthOrCoverageSideEffects(const HW::ShaderRegisters& sh_regs) {
 	const auto& db = sh_regs.db_shader_control;
 	return db.shader_kill_enable || db.shader_z_export_enable || db.shader_mask_export_enable ||
-	       db.shader_dual_export_enable || db.shader_execute_on_noop;
+	       db.shader_dual_export_enable || db.shader_execute_on_noop || sh_regs.AlphaToMask();
 }
 
 struct DrawRenderState {