Merge changes from topic "st-mmc-updates" into integration

* changes:
  feat(st-sdmmc2): define FIFO size
  feat(st-sdmmc2): make reset property optional
  feat(st): enable MMC_FLAG_SD_CMD6 for SD-cards
  feat(st-sdmmc2): manage CMD6
  feat(mmc): manage SD Switch Function for high speed mode