ffi: Add SPDX-License-Idetifier

Commit 9e2890d35e96 ("build: add liburing-ffi") didn't add
"SPDX-LIcense-Identifier" in src/ffi.c. Add it.

Cc: Christian Mazakas <christian.mazakas@gmail.com>
Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
Link: https://lore.kernel.org/r/20221219155000.2412524-2-ammar.faizi@intel.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
1 file changed