xa_destroy() frees only internal data. The caller is responsible for
freeing the exteranl objects referenced by an xarray.

Fixes: 1cf7a12e ("nvme: use an xarray to lookup the Commands Supported and Effects log")
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>