backwards: Enable Steam and let it use the 8BitDo pad

`hid_nintendo` claims the pad when it is in Nintendo Switch mode, which
leaves Steam unable to reach it through hidraw. Blacklist the module and
tag the device with `uaccess` so Steam can open it.

hosts/backwards/modules/boot/default.nix

@@ -43,6 +43,8 @@ in
         efi.canTouchEfiVariables = true;
       };
 
+      blacklistedKernelModules = [ "hid_nintendo" ];
+
       extraModprobeConfig = ''
         options snd-intel-dspcfg dsp_driver=1
         options snd_hda_intel power_save=0 power_save_controller=N