smpp: Add the classic check for osmo_fd_register

In case the osmo_fd_register will fail we will need to free the
memory we have allocated.

Fixes: Coverity CID 1042375
1 file changed
tree: 64aacfdd7585e9ec8b7f59178ec792423c104542
  1. debian/
  2. hlrsync/
  3. linux-kernel/
  4. openbsc/
  5. wireshark/
  6. README