firewire: core: fix multichannel IR with buffers larger than 2 GB

With a 32-bit i, computing i<<PAGE_SHIFT might result in
an overflow and in an eventual sign-extension.
Signed-off-by: NClemens Ladisch <clemens@ladisch.de>
Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/core-iso.c

@@ -146,7 +146,7 @@ EXPORT_SYMBOL(fw_iso_buffer_destroy);
 /* Convert DMA address to offset into virtually contiguous buffer. */
 size_t fw_iso_buffer_lookup(struct fw_iso_buffer *buffer, dma_addr_t completed)
 {
-	int i;
+	size_t i;
 	dma_addr_t address;
 	ssize_t offset;