Revert "alsa-firmware: 1.2.1 -> 1.2.4"

This was pushed to master without a PR and broke cross compilation of a
small cross-NixOS:

```
configure: error: in `/build/alsa-firmware-1.2.4':
configure: error: C compiler cannot create executables
See `config.log' for more details
```

Let's re-roll this in a PR.

This reverts commit 72f71e9.

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

@@ -1,13 +1,18 @@
 { stdenv, buildPackages, autoreconfHook, fetchurl, fetchpatch }:
 
 stdenv.mkDerivation rec {
-  name = "alsa-firmware-1.2.4";
+  name = "alsa-firmware-1.2.1";
 
   src = fetchurl {
     url = "mirror://alsa/firmware/${name}.tar.bz2";
-    sha256 = "sha256-tnttfQi8/CR+9v8KuIqZwYgwWjz1euLf0LzZpbNs1bs=";
+    sha256 = "1aq8z8ajpjvcx7bwhwp36bh5idzximyn77ygk3ifs0my3mbpr8mf";
   };
 
+  patches = [ (fetchpatch {
+    url = "https://github.com/alsa-project/alsa-firmware/commit/a8a478485a999ff9e4a8d8098107d3b946b70288.patch";
+    sha256 = "0zd7vrgz00hn02va5bkv7qj2395a1rl6f8jq1mwbryxs7hiysb78";
+  }) ];
+
   nativeBuildInputs = [ autoreconfHook buildPackages.stdenv.cc ];
 
   configureFlags = [