How to find out Processor GPIO maximum source current and maximum sink current of that pin
That is one of the most useless datasheets I have ever seen.

The maximum current levels for GPIO pins are not specified in the data sheet.  This apparently is intentional on Freescale's part.  

This question was brought up in a Freescale forum.  A Freescale employee,  Yuri Muhin answered.  In the last paragraph, he says "Maximum current levels ... are not specified."

Here is the full text of his answer:


  Re: Source and Sink Current on i.MX6 SoloLite Yuri Muhin Employee Yuri
  Muhin Apr 14, 2014 1:02 AM (in response to David Boling)
  
  There are values of load current in the Datasheet(s), which relate
  to some typical configurations, in particular - in order to guarantee
  specified output voltages. For more accurate (application depended)
  estimations IBIS models should be  applied.
  
  Really the data of i.MX Datasheets specify maximum / minimum
  voltage levels in relation with current loads. These current values
  should not be considered as maximum allowed ones, just as reasonable.
  IBIS model provides current-voltage  curves for pins in order to
  calculate real currents and voltages on pins.
  
  Another case, that corresponding voltage (high, low) levels may not
  be in ranges, shown in Datasheet and defined as logical 0 or 1. 
  
  Maximum current values (which do not decrease life time and do not
  damage the device) are not specified, because they are application
  dependent and relate to general thermal estimations. Say, if a
  separate pin can sink high current, say greater than 8 mA, this does
  not mean that all pins may be loaded (simultaneously) with such
  values. Strictly speaking the i.MX6  is not intended to be used as
  high current GPIO source or sink, assuming that special buffers or I/O
  expanders should be applied for it.
  
  Have a great day, Yuri


Have a great day, indeed.