[MTD] nandsim: Enhance nandsim optionally to report wear information

A new module parameter 'rptwear' specifies how many erases between
reporting wear information.  Zero means never.

Signed-off-by: Adrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>