dmaengine: sh: usb-dmac: Fix pm_runtime_{enable,disable}() imbalance

If the call to pm_runtime_get_sync() failed, Runtime PM was left
enabled.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>