gpu: nvgpu: increase wait time during shutdown

gpu: nvgpu: increase wait time during shutdown

In GPU shutdown path, we currently wait for 2s to allow
all other work to finish.

Increase this time to 5s as a workaround in case
2s is insufficient

This commit should be reverted once proper fixes are merged

Bug 200165480

Change-Id: I1bb99568235c327dab53114afb902507fb5f0792
Signed-off-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-on: http://git-master/r/931024
(cherry picked from commit 4d1baeff1ace5a03ee15ec1c27081d328c21f739)
Reviewed-on: http://git-master/r/1002869
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>