dmaengine: tegra-apb: Really fix runtime-pm usage

Commit edd3bdbe ("dmaengine: tegra-apb: Correct runtime-pm usage")
added pm_runtime_get/put() calls to the tegra-apb DMA system suspend
callbacks. Runtime PM is disabled during system suspend and so these
APIs cannot be used. Fix the suspend handling for the tegra-apb DMA by
moving the save and restore of the DMA register context into the
runtime PM suspend and resume callbacks, and then use the
pm_runtime_force_suspend/resume() APIs to invoke the runtime PM
callbacks during system suspend.

Fixes: edd3bdbe ("dmaengine: tegra-apb: Correct runtime-pm usage")
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>