perf/core: Don't leak AUX buffer refcount on allocation failure

Failure of the AUX buffer allocation leaks the reference count.

Set the reference count to 1 only when the allocation succeeds.

Fixes: 45bfb2e5 ("perf: Add AUX area to ring buffer for raw data streams")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: stable@vger.kernel.org