net: mdio: C22 is now optional, EOPNOTSUPP if not provided

[ Upstream commit b063b192 ]

When performing a C22 operation, check that the bus driver actually
provides the methods, and return -EOPNOTSUPP if not. C45 only busses
do exist, and in future their C22 methods will be NULL.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: 0e629694 ("net/mdiobus: Fix potential out-of-bounds read/write access")
Signed-off-by: Sasha Levin <sashal@kernel.org>