net: dwc_et_qos: update weak function board_interface_eth_init

Align the board and driver prototype for board_interface_eth_init
to avoid execution issue (the interface_type parameter is defined
as int or phy_interface_t).

To have a generic weak function (it should be reused by other driver)
I change the prototype to use directly udevice.

This prototype is added in netdev.h to allow compilation check
and avoid warning when compiling with W=1 on file
board/st/stm32mp1/stm32mp1.c

warning: no previous prototype for 'board_interface_eth_init'\
[-Wmissing-prototypes]
     int board_interface_eth_init(int interface_type, ....
         ^~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>