Reduce OpenMP thread busywait time (200 to 1 ms)

Reduce the time OpenMP threads used by Eigen busywait for new work after
completing a piece. This is 200ms by default, which meant that we tried
to continuously run 8 threads for 200ms after completing operations
using Eigen - starving both our other work and the rest of the system.

Bug: 79159165
Test: mm
Test: cherry-picked to systrace branch and look at traces
Test: NeuralNetworksTest_static
Change-Id: I3f21aea6d96c785dd7c47493a739b76876420f7d