gsm: Revert the gsm_7bit_encode changes as they are wrong

This reverts commit f996b05dbddccb8e8788dd69777a4fedfa2373eb
and 2b0cac4ef83137ee0bdd583aee877eac467abeab. A detailed
explanation can be found here:

  http://lists.osmocom.org/pipermail/openbsc/2013-July/004737.html

The short description is that:

1.) The API should return (as out parameter) the number of
    octets used.
2.) The handling for the <CR> encoding only applies to USSD
    and it is incomplete. On top of that it broke the SMS test.
2 files changed