iommu: No need to pass '0x' when '%pa' is used

Commit 6197ca82 (iommu: Use %pa and %zx instead of casting) introduced the
usage of '%pa', but still kept the '0x', which leads to printing '0x0x'.

Remove the '0x' when '%pa' is used.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>