net: phy: Add support for polling cable test

Some PHYs are not capable of generating interrupts when a cable test
finished. They do however support interrupts for normal operations,
like link up/down. As such, the PHY state machine would normally not
poll the PHY.

Add support for indicating the PHY state machine must poll the PHY
when performing a cable test.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>