gstbasedec: fix post processing invalid address error
gstbasedec: fix post processing invalid address error

if user wants to disable zero-copy implementation (i.e. use-drm=false) and use different sinks
such as kmssink/filesink/appsink. due to this need to allocate a buffer if use-drm=false to
fix the invalid address error reported by post processing module.

Signed-off-by: Sandeep Sheriker M <edd1a9544e0de4a557bbc2a542a98a5d73afd835@microchip.com>

linux4sam/gst1-hantro-g1,linux4sam/gst1-hantro-g1