Staging: VME: Update TODO file

Contents of TODO file has become more of a feature wish-list rather than issues
which should stop the VME driver being merged into the mainline kernel.

Update the TODO list with issues that need to be resolved before it can be
migrated to mainline.

Signed-off-by: Martyn Welch <martyn.welch@ge.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>