swiotlb-xen: fix late init retry

commit 4c092c5 upstream.

The commit referenced below removed the assignment of "bytes" from
xen_swiotlb_init() without - like done for xen_swiotlb_init_early() -
adding an assignment on the retry path, thus leading to excessively
sized allocations upon retries.

Fixes: 2d29960 ("swiotlb: dynamically allocate io_tlb_default_mem")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: stable@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Link: https://lore.kernel.org/r/778299d6-9cfd-1c13-026e-25ee5d14ecb3@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>

drivers/xen/swiotlb-xen.c

@@ -211,8 +211,8 @@ int __ref xen_swiotlb_init(void)
 	if (repeat--) {
 		/* Min is 2MB */
 		nslabs = max(1024UL, (nslabs >> 1));
-		pr_info("Lowering to %luMB\n",
-			(nslabs << IO_TLB_SHIFT) >> 20);
+		bytes = nslabs << IO_TLB_SHIFT;
+		pr_info("Lowering to %luMB\n", bytes >> 20);
 		goto retry;
 	}
 	pr_err("%s (rc:%d)\n", xen_swiotlb_error(m_ret), rc);