sdhci: use DEFINE_SDHCI_COMMON_PROPERTIES() for common sysbus/pci properties

Add common/sysbus/pci/sdbus comments to have clearer code blocks separation.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20180115182436.2066-4-f4bug@amsat.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>