via-velocity: Use more typical logging styles

Use netdev_<level> in place of VELOCITY_PRT.
Use pr_<level> in place of printk(KERN_<LEVEL>.

Miscellanea:

o Add pr_fmt to prefix pr_<level> output with "via-velocity: "
o Remove now unused functions and macros
o Realign some logging lines
o Remove devname where pr_<level> is also used

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