iwlwifi: dbg_ini: use function to check if ini dbg mode is on

use iwl_trans_dbg_ini_valid function instead of a boolean value check if
dbg_ini mode is on. It is needed for a future patch.

Signed-off-by: Shahar S Matityahu <shahar.s.matityahu@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>