nvme: fix incorrect sizeof

nvme: fix incorrect sizeof

The plid array, head->plids, is meant to store placement IDs, each of
type u16. But its size has been incorrectly calculated, as the size of
the pointer is being used instead of the size of the object it points
to.

Use the sizeof(*head->plids) in kcalloc so that we don't allocate extra.

Fixes: 38e8397dde63 ("nvme: use fdp streams if write stream is provided")
Reported-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
Reviewed-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>