[PATCH v2 0/4] mmc: add setdsr support

[Markus Niebel]

This is an example to add DSR support to barebox. Why this feature is
considered as useful is described in the first patch. Second and third
patch show how to pass values via device tree or platform data and 
last patch shows how this can be supported for a board using platform 
data.

Tested with TQMa53 and a 4.41 Micron eMMC with DSR support.

Changelog v1 (RFC) -> v2
- add device tree support
- fix possible null pointer access

[PATCH 1/4] mci: add DSR support
[PATCH 2/4] mci: add device tree support for DSR
[PATCH 3/4] mci: imx-esdhc: add DSR support
[PATCH 4/4] boards: tqma53: add DSR support for eMMC