dmaengine: nbpfaxi: Use dev_get_drvdata()

Using dev_get_drvdata directly.

Cc: Vinod Koul <vinod.koul@intel.com>
Cc: dmaengine@vger.kernel.org
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>