dt-binding: mmc: rename tmio_mmc.txt to renesas,sdhi.txt

As commit b6147490 ("mmc: tmio: split core functionality, DMA and
MFD glue") said, these MMC controllers use the IP from Panasonic.

TMIO (Toshiba Mobile IO) MMC was the first upstreamed user of this IP.
The common driver code was split and expanded as 'tmio-mmc-core', then
it became historical misnomer since 'tmio' is not the name of this IP.

In the discussion [1], we decide to keep this name as-is at least in
Linux driver level because renaming everything is a big churn.

However, DT should not be oriented to a particular project even though
it is mainly developed in Linux communities.

This is the misfortune only in Linux. Let's stop exporting it to other
projects, where there is no good reason to call this hardware "TMIO".
Rename the file to renesas,sdhi.txt. In fact, all the information in
this file is specific to the Renesas platform.

This commit also removes the first paragraph entirely. The DT-binding
should describe the hardware. It is strange to talk about Linux driver
internals such as how the drivers are probed, how platform data are
handed off, etc.

[1] https://www.spinics.net/lists/linux-mmc/msg46952.html



Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>