linux-firmware: fetchgit -> fetchzip

No need to do a full git clone for this.  Checked that the hash stays
the same.

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

@@ -1,12 +1,11 @@
-{ stdenvNoCC, fetchgit, lib }:
+{ stdenvNoCC, fetchzip, lib }:
 
 stdenvNoCC.mkDerivation rec {
   pname = "linux-firmware";
   version = "20220509";
 
-  src = fetchgit {
-    url = "https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git";
-    rev = "refs/tags/${version}";
+  src = fetchzip {
+    url = "https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/snapshot/linux-firmware-${version}.tar.gz";
     sha256 = "sha256-pNuKA4XigrHU9qC5Ch6HLs3/tcv0zIkAzow9VOIVKdQ=";
   };