Minor tweaks to the imx GPT timer...

Minor tweaks to the imx GPT timer...
 - Don't use spaces or dots in the eventtimer or timecounter names.
   They turn into sysctl node names, and it's just confusing.
 - Use comparator #3 instead of #1 for one-shot events.  There's an
   extra 1-cycle penalty in the hardware for accessing the registers
   for comparator 1, no point in paying that penalty.
 - Lower the quality of the eventtimer from 1000 to 800, because the
   device can't support PERCPU timers and some other device in the system
   may be able to provide that.