dereferencing freed memory regulator_fixed_voltage_remove()

Don't dereference drvdata after it has been freed.

regards,
dan carpenter

Signed-off-by: Dan Carpenter <error27@gmail.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>