OMXNodeInstance: Allow dynamic native handle for shared mem buffer

* Change Ief2d2d4d0445074c0ecdc723b1b25997a7631389, part of Aug 2018
  ASB, authored to mitigate CVE-2018-9427, restricted useBuffer()
  based on buffer type and port mode.
* Follow-up change I1e4eb72e070f4e60ff4df94f9b9d161361828477 allowed
  dynamic handles for input buffers, but not a *native* handle for
  this specific buffer type.
* Some of our devices using legacy HAL1 recording require this
  combination of buffer type and port mode, so allow when explicitly
  requested.

Change-Id: I15f8cbb3956773e2ba97032203f5e9254505d8ac