n_gsm: Copy n2 over when configuring via ioctl interface

The n2 field is settable but didn't get propogated

Signed-off-by: Ken Mills <ken.k.mills@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>