net: phy: dp83867: Fix device tree entries

Fix the device tree entries to modify the '_' to '-'.
Also changes the names of the internal delay properties
from -int- to -internal- as the -int- appeared as a keyword.

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