mmc: sdhi, tmio: only check flags in tmio-mmc driver proper

tmio-mmc platform flags can be set by various means, including caller
drivers and device-tree bindings, therefore it is better to only check
them in the tmio-mmc driver proper, not in caller drivers themselves.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Chris Ball <cjb@laptop.org>