mfd: Fix error handling if BUG() isn't enabled in WM8994

Even if we would've BUG()ed we should still tidy up after ourselves if that
isn't enabled in the kernel config.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
1 file changed