vfio: reformat logs

vfio: reformat logs

The log messages had various issues:
- split on 2 lines, making search (grep) difficult
- long lines (can be split after the string)
- indented for no good reason (parent message may have higher log level)
- inconsistent use of __func__, not meaningful context for user
- lack of context (general message not mentioning VFIO)
- log level too high (more below)

Message having its level decreased from WARNING to NOTICE:
	"not managed by VFIO driver, skipping"
Message having its level decreased from INFO to DEBUG:
	"Probing VFIO support..."

Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>