common: phys_mem_meta: also copy meta when buffer and physical memory copied

... so as to support zero-copy buffer metadata copies in tee'd pipelines.
v4l2src: bufferpool: allow shared memory in buffers
v4l2src: only 1 bufferpool should be around, also during re-allocation

... when so triggered by a downstream (post-tee) element.
Merge pull request #13 from mnauw/tee-support

Tee support