video: atmel_lcdfb: Use common error handling code in atmel_lcdfb_of_init()

[SF Markus Elfring]

> Sorry but NACK: the message was malformed and resulted in the
> duplication of the error log that you spotted.
> 
> The proper way to fix this is to modify the second occurrence of this message.

* Would you like to achieve that a corresponding message will mention
  anything around a property “atmel,dmacon” (instead of “bits-per-pixel”)?

* Can it make sense to adjust the used message format then?

Regards,
Markus