ath: change logging functions to return void

The return values are not used by callers of these functions
so change the functions to return void.

Other miscellanea:

o add __printf verification to wil6210 logging functions
  No format/argument mismatches found

Acked-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>