linuxPackages.netatop: fix build with Linux 5.18

With 5.18, implicit fallthrough is an error, and netatop hasn't caught
up yet.

pkgs/os-specific/linux/netatop/default.nix

···
   buildInputs = [ kmod zlib ];
 
   hardeningDisable = [ "pic" ];
+  NIX_CFLAGS_COMPILE = [ "-Wno-error=implicit-fallthrough" ];
 
   patches = [
     # fix paths in netatop.service