msdk: fix dec alignment
It is possible that the output region size (e.g. 192x144) is different from the coded picture size (e.g. 192x256). We may adjust the alignment parameters so that the padding is respected in GstVideoInfo and use GstVideoInfo to calculate mfx frame width and height
This fixes the error below when decoding a stream which has different
output region size and coded picture size
0:00:00.057726900 28634 0x55df6c3220a0 ERROR msdkdec
gstmsdkdec.c:1065:gst_msdkdec_handle_frame:<msdkh265dec0>
DecodeFrameAsync failed (failed to allocate memory)
Sample pipeline:
gst-launch-1.0 filesrc location=output.h265 ! h265parse ! msdkh265dec !
glimagesink