net: phy: Port set/clear bits from Linux

net: phy: Port set/clear bits from Linux

To simply porting phy drivers from Linux to U-Boot, define
phy_set_bits() and phy_clear_bits() functions with a similar API to
those used in Linux.

The U-Boot versions of these functions include the `devad` argument
which is not present in the Linux versions, to keep them aligned with
the other phy functions in U-Boot.

Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>