nvme-pci: avoid hmb desc array idx out-of-bound when hmmaxd set.

hmb descriptor idx out-of-bound occurs in case of below conditions.
preferred = 128MiB
chunk_size = 4MiB
hmmaxd = 1

Current code will not allow rmmod which will free hmb descriptors
to be done successfully in above case.

"descs[i]" will be set in for-loop without seeing any conditions
related to "max_entries" after a single "descs" was allocated by
(max_entries = 1) in this case.

Added a condition into for-loop to check index of descriptors.

Fixes: 044a9df1("nvme-pci: implement the HMB entry number and size limitations")
Signed-off-by: Minwoo Im <minwoo.im.dev@gmail.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/pci.c

@@ -1787,7 +1787,7 @@ static int __nvme_alloc_host_mem(struct nvme_dev *dev, u64 preferred,
 	if (!bufs)
 		goto out_free_descs;
 
-	for (size = 0; size < preferred; size += len) {
+	for (size = 0; size < preferred && i < max_entries; size += len) {
 		dma_addr_t dma_addr;
 
 		len = min_t(u64, chunk_size, preferred - size);