AM35x MMC 2 controller has internal clock loopback setting which cannot
be utilized without this patch and thus SDIO devices connected to this
controller and depend on this setting will fail to initialize.
Signed-off-by: NIgor Grinberg <grinberg@compulab.co.il>
[tony@atomide.com: updated comments]
Signed-off-by: NTony Lindgren <tony@atomide.com>