vdec: update buffer len based on crop size
vdec: update buffer len based on crop size

H.264 can have resolutions not multiples of 16, in which case the
videosink would expect buffers to be of the size of the video to be
rendered, and not bigger.

Signed-off-by: Felipe Contreras <de77a8b9cd239b204c19c52ed62e48ab47243362@nokia.com>

community-ssu/gst-dsp,felipec/gst-dsp,community-ssu/gst-dsp,community-ssu/gst-dsp,felipec/gst-dsp