mfd: Clean timberdale error handling code up

In the first three cases, ioremap has been called, so iounmap is needed.  A
new label for this is introduced, to differentiate it from err_msix, which
is the first point at which msix_entries actually needs to be freed.

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>