net: mscc: Fix non-GPL export of regmap APIs

The ocelot driver makes use of regmap, wrapping it with driver specific
operations that are thin wrappers around the core regmap APIs. These are
exported with EXPORT_SYMBOL, dropping the _GPL from the core regmap
exports which is frowned upon. Add _GPL suffixes to at least the APIs that
are doing register I/O.

Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>