swiotlb: Use %pa to print phys_addr_t variables

There is an extension to a %p to print phys_addr_t type of variables.
Use it here.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>