Was:
* wrong memset
* double free
* use of uninitialized variable

issue #10

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Signed-off-by: Federico Vaga <federico.vaga@cern.ch>

This top-level driver was expecting a special driver version. When
working with the standard driver it was crashing due to a NULL pointer
for the DMA resource.

This patch fixes the error condition by using the resources only when
it's found, otherwise it silently continue.
Signed-off-by: Federico Vaga <federico.vaga@cern.ch>

Signed-off-by: Federico Vaga <federico.vaga@cern.ch>