Move libdvr.google into system_ext

it is not a part of the system according to
generic_system.mk.

Bug: 173538619
Bug: 167689596
Test: presubmit
Signed-off-by: Roman Kiryanov <rkir@google.com>
Change-Id: Ia9fa2dd8feba10056c4b88b3bfb1e386c58f7a54