board: ti: am335x: add support to fixup phy address

board: ti: am335x: add support to fixup phy address

On beaglebone black, it can so happen that PHY address
is not latched correctly on reset and board boots with
PHY responding to a different address than that
programmed in device-tree. For example, see this report:

https://groups.google.com/d/msg/beagleboard/9mctrG26Mc8/1FuI_i5KW10J

Workaround this by fixing up device-tree passed to kernel
by using the PHY address detected in hardware.

Beaglebone itself uses only one ethernet port and its DT
currently uses phy_id (obsoleted). But the function has
been written to handle multiple ports and phy_id as well
as phy-handle to make the function more generically useful.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>