leds-as3645a: Drop fwnode reference on ignored node

If a node is ignored, do not get a reference to it. Fix the bug by moving
fwnode_handle_get() where a reference to an fwnode is saved for clarity.

Reported-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Pavel Machek <pavel@ucw.cz>