net: phy: dp83867: Fix various styling and space issues

Fix spacing issues reported for misaligned switch..case and extra new
lines.

Also updated the file header to comply with networking commet style.

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Dan Murphy <dmurphy@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>