pass deviceType when running smartctl data collection (for megaraid type disks).

Make DevicePrefix a public function available outside the detect module.
if device type is detected as "ata" or "scsi", dont pass in via -d parameter, can cause issues with missing data.

collector/pkg/detect/devices_linux.go

@@ -5,7 +5,7 @@ import (
 	"github.com/jaypipes/ghw"
 )
 
-func (d *Detect) devicePrefix() string {
+func DevicePrefix() string {
 	return "/dev/"
 }