nixos/sd-image-*.nix: Bring back high consoleLogLevel

3d040f93051866 removed it from installation-device.nix, but the default
loglevel is just too low for ARM and the like.

nixos/modules/installer/cd-dvd/sd-image-aarch64.nix

···
   boot.loader.grub.enable = false;
   boot.loader.generic-extlinux-compatible.enable = true;
 
+  boot.consoleLogLevel = lib.mkDefault 7;
   boot.kernelPackages = pkgs.linuxPackages_latest;
 
   # The serial ports listed here are:

nixos/modules/installer/cd-dvd/sd-image-armv7l-multiplatform.nix

···
   boot.loader.grub.enable = false;
   boot.loader.generic-extlinux-compatible.enable = true;
 
+  boot.consoleLogLevel = lib.mkDefault 7;
   boot.kernelPackages = pkgs.linuxPackages_latest;
   # The serial ports listed here are:
   # - ttyS0: for Tegra (Jetson TK1)

nixos/modules/installer/cd-dvd/sd-image-raspberrypi.nix

···
   boot.loader.grub.enable = false;
   boot.loader.generic-extlinux-compatible.enable = true;
 
+  boot.consoleLogLevel = lib.mkDefault 7;
   boot.kernelPackages = pkgs.linuxPackages_rpi;
 
   # FIXME: this probably should be in installation-device.nix