Documentation/development-process: more staging info

Document things that I would've liked to have known when submitting a driver
to gregkh for staging.

Signed-off-by: Andres Salomon <dilinger@queued.net>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>