x86/platform/intel-mid: Add empty stubs for intel_scu_devices_[create|destroy]()

This allows to call the functions even when CONFIG_X86_INTEL_MID is not
enabled.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>