nvme-pci: compile warnings in nvme_alloc_host_mem()

"i" should be signed or it could cause a forever loop on the cleanup
path. "size" can be used uninitialized.

Fixes: 87ad72a59a ("nvme-pci: implement host memory buffer support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>

drivers/nvme/host/pci.c

@@ -1582,9 +1582,10 @@ static void nvme_free_host_mem(struct nvme_dev *dev)
 static int nvme_alloc_host_mem(struct nvme_dev *dev, u64 min, u64 preferred)
 {
 	struct nvme_host_mem_buf_desc *descs;
-	u32 chunk_size, max_entries, i = 0;
+	u32 chunk_size, max_entries;
+	int i = 0;
 	void **bufs;
-	u64 size, tmp;
+	u64 size = 0, tmp;
 
 	/* start big and work our way down */
 	chunk_size = min(preferred, (u64)PAGE_SIZE << MAX_ORDER);