leds: Use log level warn instead of info when telling about a name clash

The LED names are expected to be unique in the system. Use KERN_WARNING log
level to notify the user about the matter.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>