MFC: r276469

• Switching the mode of Ricoh R5CE823 to SD2.0 causes their PCI device ID to change to 0xe822, which may be persistent across reboots and, thus, confuse other OSes. Therefore, restore the original mode and frequency setting on detach and shutdown.
• Report Ricoh R5CE822 as such.
• According to Linux, Ricoh R5CE822 also need SDHCI_QUIRK_LOWER_FREQUENCY.
• Nuke an unused softc member.