Revert "media: subdev: disallow ioctl for saa6588/davinci"

This reverts commit db317a37 as it
breaks the ABI and is not needed for Android devices at this point in
time.

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I060fe0a18cc6232f82fa4d3dd0426262a71aaccf