net: aquantia: atlantic: remove declaration of hw_atl_utils_hw_set_power

This function is not defined, so no need to declare it.

As I don't have the hardware, I'd be very pleased if
someone may test this patch.

Signed-off-by: Philippe Reynes <tremyfr@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>