After set PROBE_PREFER_ASYNCHRONOUS flag on the mmc host drivers,
the order of /dev/mmcblkN was not fixed in some SoCs which have
multiple SDHI and/or MMCIF controllers. So, we were hard to use
such a device as rootfs by using the kernel parameter like
"root=/dev/mmcblkNpM".

According to the discussion on a mainling list [1], we can add
mmc aliases to fix the issue. So, add such aliases into R-Car Gen2
board dts files. Note that, since R-Car Gen2 is even more complicated
about SDHI and/or MMCIF channels variations and they share pins,
add the aliases into board dts files instead of SoC dtsi files.

[1]
https://lore.kernel.org/linux-arm-kernel/CAPDyKFptyEQNJu8cqzMt2WRFZcwEdjDiytMBp96nkoZyprTgmA@mail.gmail.com/

Fixes: 7320915c ("mmc: Set PROBE_PREFER_ASYNCHRONOUS for drivers that existed in v4.14")
Fixes: 21b2cec6 ("mmc: Set PROBE_PREFER_ASYNCHRONOUS for drivers that existed in v4.4")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/1613131316-30994-1-git-send-email-yoshihiro.shimoda.uh@renesas.comSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>