of: use pr_fmt prefix for all console printing

of: use pr_fmt prefix for all console printing

Clean-up all the DT printk functions to use common pr_fmt prefix.

Some print statements such as kmalloc errors were redundant, so just
drop those.

Cc: Frank Rowand <[email protected]>
Cc: Pantelis Antoniou <[email protected]>
Reviewed-by: Frank Rowand <[email protected]>
Signed-off-by: Rob Herring <[email protected]>