net: stmmac: dwmac-rk: remove unused gpio register defines

In a first version the driver did want to do some gpio wiggling, which
of course never made it into the kernel, but somehow these register
defines where forgotten. Remove them, as they shouldn't be here.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: David S. Miller <davem@davemloft.net>