spi: dw-pci: Add runtime power management support

Implement pm_runtime hooks at pci driver.

Signed-off-by: Raymond Tan <raymond.tan@intel.com>
[jarkko.nikula@linux.intel.com: Forward ported on top of
commit 1e6959832510 ("spi: dw: Add basic runtime PM support")]
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Link: https://lore.kernel.org/r/20191018132131.31608-2-jarkko.nikula@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>