swiotlb-xen: fix late init retry

swiotlb-xen: fix late init retry

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: 2d29960af0be ("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>
Link: https://lore.kernel.org/r/778299d6-9cfd-1c13-026e-25ee5d14ecb3@suse.com
Signed-off-by: Juergen Gross <jgross@suse.com>