staging: dgap: fixes incompatible type error

This patch fixes the error: incompatible types
when assigning to type ‘struct ktermios *’ from
type ‘struct ktermios’

Signed-off-by: Lidza Louina <lidza.louina@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>