spi: dw-pci: Use dev_get_drvdata

Instead of using to_pci_dev + pci_get_drvdata,
use dev_get_drvdata to make code simpler.

Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Link: https://lore.kernel.org/r/20190724122331.21856-1-hslester96@gmail.com


Signed-off-by: Mark Brown <broonie@kernel.org>