net: stmmac: mdio: provide priv->gmii_address_bus_config

net: stmmac: mdio: provide priv->gmii_address_bus_config

Provide a pre-formatted value for the MDIO address register fields
which remain constant across the various different transactions
rather than recreating the register value from scratch every time.
Currently, we only do this for the CR (clock range) field.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Mohd Ayaan Anwar <quic_mohdayaa@quicinc.com>
Link: https://patch.msgid.link/E1uu8o2-00000001vog-1LyK@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>