misc: ocxl: fix possible refcount leak in afu_ioctl()

eventfd_ctx_put need to be called to put the refcount that gotten by
eventfd_ctx_fdget when ocxl_irq_set_handler fails.

Fixes: 06014661 ("ocxl: move event_fd handling to frontend")
Acked-by: Frederic Barrat <fbarrat@linux.ibm.com>
Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
Link: https://lore.kernel.org/r/20220824082600.36159-1-hbh25y@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>