First part is to assign default argument for all cases, since
bias disablement doesn't use it anyway.

Second part is to clear all bits in the bias setting and
depending on the argument and parameter set them as asked.

While at it, add break statement to the default cases.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>