ecryptfs: remove debug as mount option, and warn if set via modprobe

ecryptfs_debug really should not be a mount option; it is not per-mount,
but rather sets a global "ecryptfs_verbosity" variable which affects all
mounted filesysytems.  It's already settable as a module load option,
I think we can leave it at that.

Also, if set, since secret values come out in debug messages, kick
things off with a stern warning.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Acked-by: Mike Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>