TODO:
- support more pcie card reader of Realtek family
- use kernel coding style
- checkpatch.pl fixes
- stop having thousands of lines of code duplicated with staging/rts5139
- This driver contains an entire SD/MMC stack -- it should use the stack in
  drivers/mmc instead, as a host driver e.g. drivers/mmc/host/realtek-pci.c;
  see drivers/mmc/host/via-sdmmc.c as an example.
- This driver presents cards as SCSI devices, but they should be MMC devices.