sgsn: Fix logically dead code in regard to the osmo_fd_register

The code was written like checking the return value of the
osmo_fd_register but the rc variable was not assigned for the
subsequent calls.

Fixes: Coverity CID 1040741
1 file changed
tree: f7512dc570dc9de0b1e6c09b25faf450c9ea3ba5
  1. debian/
  2. hlrsync/
  3. linux-kernel/
  4. openbsc/
  5. wireshark/
  6. README