mid_pmu: remove forever loop while shutdown in progress

mid_pmu: remove forever loop while shutdown in progress

BZ: 31284

DUT hangs while ctrl-alt-del key is pressed, this is
caused because of a forever loop in pmu_pci_set_power_state
that was used to block d0ix commands from causing IPC commands
blocking the shutdown process.

Now that we have removed the restriction of IPC/PMU command
synchrnoization this can also be removed.

Acknowledgement:
Tu, Xiaobing <xiaobing.tu@intel.com> root caused this issue.

Change-Id: I6bd4762a65d3e77c7d130660d831bb1297730eb6
Signed-off-by: Illyas Mansoor <illyas.mansoor@intel.com>
Tested-by: Tu, Xiaobing <xiaobing.tu@intel.com>
Reviewed-on: http://android.intel.com:8080/47722
Reviewed-by: Gross, Mark <mark.gross@intel.com>
Reviewed-by: Yang, Fei <fei.yang@intel.com>
Reviewed-by: Cuesta, FernandX <fernandx.cuesta@intel.com>
Tested-by: Cuesta, FernandX <fernandx.cuesta@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>