scalapack: update meta data

* Set platform from linux -> x86_64-linux
Scalapack does not seem to run properly on ARM (failing tests)

* Add markuskowa as maintainer

pkgs/development/libraries/science/math/scalapack/default.nix

···
     homepage = http://www.netlib.org/scalapack/;
     description = "Library of high-performance linear algebra routines for parallel distributed memory machines";
     license = licenses.bsd3;
-    platforms = platforms.linux;
-    maintainers = [ maintainers.costrouc ];
+    platforms = [ "x86_64-linux" ];
+    maintainers = with maintainers; [ costrouc markuskowa ];
   };
 
 }