Comment # 2 on bug 998440 from Giacomo Comes

I have done more testing. Finally on this laptop the minimum requirement
in order to have the mmc card reader working is to simply add the module
pinctrl-cherryview in the initrd. If I want that the mmc card is accessible
also
while the initrd is mounted as the root filesystem, then I need to add the
module sdhci-pci too.
To achieve that I created a file in /etc/dracut.conf.d containing:
  add_drivers+=" pinctrl-cherryview"
or
  add_drivers+=" pinctrl-cherryview sdhci-pci"
There is no need to force the loading of the module or to add softdep 
in modprobe.d.