gpu: nvgpu: Power on platform deps for wfi

gpu: nvgpu: Power on platform deps for wfi

Currently gk20a_channel_idle() drops pm_runtime references to gk20a
and then drops platform dependencies. As we usually delay powering down
gk20a, we may end up to case where the platform dependencies are
turned off at the moment we start powering down gk20a. Power off
sequence may use platform dependencies for informing completion of
the last work, wait-for-idle, and therefore we may simply drop the
information about job completion.

This patch adds missing calls to power up platform dependencies for
the time we submit the last work.

Bug 1484824

Change-Id: I058febc717a1cb1cf96964ce20fb807bc876be6c
Signed-off-by: Arto Merilainen <amerilainen@nvidia.com>
Reviewed-on: http://git-master/r/396286
(cherry-picked from commit 42eef2de7874f72dab36d406bdc8303f9f9bba24)
Reviewed-on: http://git-master/r/396424
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>
Reviewed-by: Automatic_Commit_Validation_User