net: dsa: microchip: add support for regmap_access_tables

This is complex driver with support for different chips with different
layouts. To detect at least some bugs earlier, we should validate register
accesses by using regmap_access_table support.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>