iwlwifi: update levels of debug prints

This patch updates the levels of debug prints, leaving only one level
in each debug print.
It was anoying and caused unnecessary prints on hot path.

Signed-off-by: Ester Kummer <ester.kummer@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>