The H264 encoder on some Huawei devices doesn't take care of row strides information
provided by MediaImage object. That resulted on bad pixel conversion
while input raw pictures were copied into the encoder input buffer.

The workaround is to assume that the encoder take yuv420p pictures
as input and thus to copy each picture in the input buffer without
any pixel format conversion.

This workaround is only applied on Huawei GRA-L09 and VNS-L31 for now.

(cherry picked from commit 15d67ea3)