net: mscc: ocelot: move the HSIO header to include/soc

Since HSIO address space can be used by different drivers (PLL, SerDes
muxing, temperature sensor), let's move it somewhere it can be included
by all drivers.

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Quentin Schulz <quentin.schulz@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>