swiotlb: consolidate swiotlb info message printing

Impact: clean up swiotlb printks

Remove duplicated swiotlb info printing, and make it more detailed.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>