ipc: freebsd: avoid leaking memory in kernel_get_device()

ipc: freebsd: avoid leaking memory in kernel_get_device()

Primarily, front-load validation of an allowed-ip entry to before we
allocate `aip`, so that we don't need to free() it if we end up skipping
this entry.  Assert that `aip` is NULL after we exit the loop, as we
should have transfered ownership to the `peer` or freed it in all paths
through the allowed-ip loop.

FreeBSD-Coverity:	1500405
Signed-off-by: Kyle Evans <kevans@FreeBSD.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>