net: mscc: ocelot: move resource ioremap and regmap init to common code

Let's make this ioremap and regmap init code common.  It should not
be platform dependent as it should be usable by PCI devices too.
Use better names where necessary to avoid clashes.

Signed-off-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>