staging: dgap: Remove dead sniff buffer code

The sniff buffer was a /proc filesystem file. This
module no longer uses /proc. This patch removes
the deaed code associated with the sniff buffer.

Signed-off-by: Mark Hounschell <markh@compro.net>
Tested-by: Mark Hounschell <markh@compro.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>