net: dsa: microchip: add ksz_rmw8() function

Add ksz_rmw8(), it will be used in the next patch.
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Acked-by: Arun Ramadoss <arun.ramadoss@microchip.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/dsa/microchip/ksz_common.h

@@ -454,6 +454,11 @@ static inline int ksz_write64(struct ksz_device *dev, u32 reg, u64 value)
 	return regmap_bulk_write(dev->regmap[2], reg, val, 2);
 }
 
+static inline int ksz_rmw8(struct ksz_device *dev, int offset, u8 mask, u8 val)
+{
+	return regmap_update_bits(dev->regmap[0], offset, mask, val);
+}
+
 static inline int ksz_pread8(struct ksz_device *dev, int port, int offset,
 			     u8 *data)
 {