cardhu: set default i/o scheduler to ROW

* Performance is much better, and less laggy. ROW is designed to
  give read's priority over writes, without breaking writes

  The ROW I/O scheduler gives priority to READ requests over the WRITE
  requests when dispatching, without starving WRITE requests.
  Requests are kept in priority queues. Dispatching is done in a RR
  manner when the dispatch quantum for each queue is calculated
  according to queue priority. Most suitable for mobile devices.

Change-Id: I9d7c404e07ac691559e8d30e68fdfd11275f2fd7