mmc: sdhci-iproc: Add ACPI bindings for the RPi

The RPi4 has an Arasan controller it carries over from the RPi3 and a newer
eMMC2 controller.  Because of a couple of quirks, it seems wiser to bind
these controllers to the same driver that DT is using on this platform
rather than the generic sdhci_acpi driver with PNP0D40.

So, BCM2847 describes the older Arasan and BRCME88C describes the newer
eMMC2. The older Arasan is reusing an existing ACPI _HID used by other OSes
booting these tables on the RPi.

With this change, Linux is capable of utilizing the SD card slot, and the
Wi-Fi when booted with UEFI+ACPI on the RPi4.

Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20210120000406.1843400-2-jeremy.linton@arm.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>