swiotlb-xen: avoid double free

Of the two paths leading to the "error" label in xen_swiotlb_init() one
didn't allocate anything, while the other did already free what was
allocated.

Fixes: b8277600 ("xen/swiotlb: Use the swiotlb_late_init_with_tbl to init Xen-SWIOTLB late when PV PCI is used")
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/ce9c2adb-8a52-6293-982a-0d6ece943ac6@suse.com


Signed-off-by: Juergen Gross <jgross@suse.com>