Use the same Linux kernel on my laptop and desktop

I no longer need to use non-default kernel version on my laptop (no more
black screen issue). NixOS default kernel is now 3.4.x which works just
fine.

And just for the record, Linux 3.2.x (old default version) is now at
version 3.2.51 and that also works on my laptop. I think the issue was
fixed in 3.2.46. See stable kernel changelog:

  https://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.2.46

And the upstream mainline commit:

  https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c8f6d8351ba8c89d5cd4c562552ec7ec29274e31