mfd: intel-lpss: Fix build error when !CONFIG_PM_SLEEP

Jim Davis reported the compilation error with a random configuration which
apparently has CONFIG_PM=y and CONFIG_PM_SLEEP=n. With that conditions we have
missed definition of INTEL_LPSS_SLEEP_PM_OPS macro. Add it here.

Reported-by: Jim Davis <jim.epost@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>