platform/x86: intel_pmc_core_pltdrv: Module removal warning fix

Prior to this commit, removing the intel_pmc_core_pltdrv module
would cause the following warning:

  Device 'intel_pmc_core.0' does not have a release() function, it is broken and must be fixed. See Documentation/kobject.txt.
  WARNING: CPU: 0 PID: 2202 at drivers/base/core.c:1238 device_release+0x6f/0x80

This commit hence adds an empty release function for the driver.

Signed-off-by: M. Vefa Bicakci <m.v.b@runbox.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>