VME: Return -EBUSY when DMA list in use

The VME subsystem currently returns -EBUSY when trying to free a DMA
resource that is busy, but returns -EINVAL when trying to free a DMA list
that is in use. Switch to returning -EBUSY when trying to free a DMA list
that is in use for consistency and correctness.

Signed-off-by: Martyn Welch <martyn@welchs.me.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>