mmc: sdhci-pci: Conditionally compile pm sleep functions

It is confusing to have some parts of suspend / resume under conditional
compilation and some parts not. Use conditional compilation everywhere.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Ludovic Desroches <ludovic.desroches@microchip.com>