regulator: fan53555: Use of_device_get_match_data() to simplify probe

if fan53555_regulator_probe() is called and the "client->dev.of_node"
isn't NULL, it means OF registered a device with a valid compatible
string, so match cannot be NULL.

Use of_device_get_match_data() to retrieve the drvdata pointer.  No
functional change intended.

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Signed-off-by: Mark Brown <broonie@kernel.org>