sgsn: Check the return value of osmo_fd_register

We can't do much in case the fd is failing to be registered.
There should be a timeout that is catching this and it might
be able to repair it self.

Fixes: Coverity CID#1302854
1 file changed
tree: 28082b6fac5c09529c7f9c41d574bb397b0ae9c9
  1. debian/
  2. hlrsync/
  3. linux-kernel/
  4. openbsc/
  5. wireshark/
  6. .gitignore
  7. README