Add LEDs blink_set() support to qca8k Switch Family.
These LEDs support hw accellerated blinking at a fixed rate
of 4Hz.
Reject any other value since not supported by the LEDs switch.
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com> Reviewed-by: Andrew Lunn <andrew@lunn.ch> Acked-by: Pavel Machek <pavel@ucw.cz> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>