mfd: intel-lpss: Release IDA resources

ida instances allocate some internal memory for ->free_bitmap
in addition to the base 'struct ida'. Use ida_destroy() to release
that memory at module_exit().

Fixes: 4b45efe8 ("mfd: Add support for Intel Sunrisepoint LPSS devices")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>