mfd: Fix double free in wm8350 error path

Fix double free in probe error path introduced by the recent conversion
of wm8350 to use regmap.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>