net: usb: lan78xx: Rename lan78xx_phy_wait_not_busy to lan78xx_mdiobus_wait_not_busy

net: usb: lan78xx: Rename lan78xx_phy_wait_not_busy to lan78xx_mdiobus_wait_not_busy

Rename `lan78xx_phy_wait_not_busy` to `lan78xx_mdiobus_wait_not_busy`
for clarity and accuracy, as the function operates on the MII bus rather
than a specific PHY. Update all references to reflect the new name.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20241209130751.703182-11-o.rempel@pengutronix.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>