net: phy: marvell: Add support for offloading LED blinking

Add the code needed to indicate if a given blinking pattern can be
offloaded, to offload a pattern and to try to return the current
pattern.

Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Daniel Golle <daniel@makrotopia.org>
Link: https://lore.kernel.org/r/20230808210436.838995-4-andrew@lunn.ch


Signed-off-by: Jakub Kicinski <kuba@kernel.org>