Revert "gpu: nvgpu: add lock for priv_cmd_queue list accesses"

Revert "gpu: nvgpu: add lock for priv_cmd_queue list accesses"

This reverts commit 21b7595b0ca4d3931b73246eb0f4fd3665379a2b.

Original patch introduces variance in nvgpu submit times

Also, it should be fine to remove the lock since the races
it protects will also be removed with revert patch
http://git-master/r/#/c/1145914/

Hence revert this patch

Bug 1755244

Change-Id: I588e2217477e5e6daea11a28021b419acdddb143
Signed-off-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-on: http://git-master/r/1145913
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>