niu: Use pr_<level>, netdev_<level> and netif_<level> macros

Remove #define PFX
Add pr_fmt(fmt) KBUILD_MODNAME ": " fmt
Convert printks to pr_<level>
Convert printks without levels to pr_cont
Convert pr_<level> with np->dev to netdev_<level>
Convert dev_<level> to netdev_<level>
Convert niudbg to netif_printk
Convert niuinfo, niuwarn macros to netif_<level>(priv, type, dev...
Coalesce long formats
Convert embedded function names to "%s", __func__
Always use "%s()..." when __func__ is printed

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>