intel_scu_ipc: Drop to C6s0i0 when there is IPC communication ongoing

intel_scu_ipc: Drop to C6s0i0 when there is IPC communication ongoing

BZ: 8911

When a IPC command is issued the IPC driver waits for the completion
interrupt from the SCU by issuing a wait_for_competion_timeout API
this causes the IPC driver to sleep, invoking idle process, which then
triggers S0ix, this causes the SCU to disable the interrupts and the
pending IPC completion interrupt is never delivered this causes
IPC timeout to occur.

Fixed this by not doing S0ix by using PM Qos which prevents any deeper
than C6 states from happening. This restrictioin is removed once the
IPC command completes.

Change-Id: I97136b131c1d6019e505e1ab97ec67cec1a473d9
Signed-off-by: Samu Onkalo <samu.onkalo@intel.com>
Signed-off-by: Illyas Mansoor <illyas.mansoor@intel.com>
Signed-off-by: Marie-Celine Dubut <marie.celinex.dubut@intel.com>
Reviewed-on: http://android.intel.com:8080/17210