staging: mt7621-mmc: Remove unnecessary setting of dev.platform_data

In the probe function, pdev->dev.platform_data is set to &msdc0_hw,
but the only get access to that is also in the probe function. So that
assignment is removed. The msdc0_hw structure is still available to the
driver as part of the msdc_host structure.

Signed-off-by: Christian Lütke-Stetzkamp <christian@lkamp.de>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>