OMXVideoDecoderBase: call renderDone in processOutPortBuffers

it is incorrect to call renderDone() in PreFillBuffer.
    a) rendering hasn't been done yet
    b) two threads may come here twice:
        there are ComponentBase::Work->OMXVideoDecoderBase::getDecodedBuffer and ComponentBase::CBaseFillThisBuffer
        calling renderDone() twice will confuse codec, since codec usually recycle surface buffer upon this call.

clear pPlatformPrivate after renderDone(), since it has been returned back to codec.
it disclose the issue of flagNativeBuffer in ProcessorPreFillBuffer, fix it.

Change-Id: I48222fd769ff7cc5c5cf8591c89b51ffff4b0721
Re-sent the H264 buffer when format change detected

When format change detected for AVC, apply same policy
as VP8 does, to sent the current stream buffer to decoder
again after flush, this aims to avoid lost of IDR frame
for reference.

Signed-off-by: Li Xiaowei <xiaowei.a.li@intel.com>