Revert "mmc: davinci_mmc: Convert to platform remove callback returning void"

This reverts commit c4f8e95a which is
commit bc1711e8 upstream.

It breaks the Android kernel build and is not needed.

Change-Id: Id9bf8d2f6b1bfc1799f0d127dad18d7f6ccbd633
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>