net: phy: fill in missing MODULE_DESCRIPTION()s

W=1 builds now warn if a module is built without a
MODULE_DESCRIPTION(). Fill them in based on the Kconfig text, or
similar.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Acked-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/20231028184458.99448-2-andrew@lunn.ch
Signed-off-by: Jakub Kicinski <kuba@kernel.org>