dt-bindings: dp83869: Fix the type of device

DP83869 is an Ethernet PHY, not a charger, so fix the documentation
accordingly.

Fixes: 4d66c56f

 ("dt-bindings: net: dp83869: Add TI dp83869 phy")
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Acked-by: Dan Murphy <dmurphy@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>