virtio: checkpatch cleanups

virtio: checkpatch cleanups

This fixes style problems reported by checkpatch including:
  * extra whitespace
  * spaces before tabs
  * strings broken across lines
  * excessively long lines
  * missing spaces after keywords
  * unnecessary paren's in return statements

Signed-off-by: Stephen Hemminger <shemming@brocade.com>
Acked-by: Changchun Ouyang <changchun.ouyang@intel.com>