net: phy: leds: Refactor "no link" handler into a separate function

Currently, phy_led_trigger_change_speed() is handling a "no link" condition
like it was some kind of an error (using "goto" to a code at the function
end).

However, having no link at PHY is an ordinary operational state, so let's
handle it in an appropriately named separate function so it is more obvious
what the code is doing.

Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Signed-off-by: David S. Miller <davem@davemloft.net>