samsung-unified-linux-driver (cups driver): patch all filters

ppd files in the `samsung-unified-linux-driver`
package invoke these filter commands:

* pstosecps
* pstospl
* rastertospl
* pstosplc

The paths to all of those commands excluding the last one got
patched with their absolute paths during the build process.
This commit adds the last one to
the list of commands to be patched.

pkgs/misc/cups/drivers/samsung/4.01.17.nix

···
     cp -r ./* $out/share/cups/model/samsung
   '';
 
-  ppdFileCommands = [ "pstosecps" "pstospl" "rastertospl" ];
+  ppdFileCommands = [
+    "pstosecps"
+    "pstospl"
+    "pstosplc"
+    "rastertospl"
+  ];
 
   meta = with lib; {
     description = "Samsung's Linux printing drivers; includes binaries without source code";