sdm: Set SDM_EventThread as RealTime task with lowest priority

SDM_EventThread is very sensitive to any delay introduced by Runnable
state because if the next complete_commit starts during it's Runnable
state, then the VSYNC registration gets pushed out to next HW Vsync
boundary. Set SDM_EventThread as RealTime task with lowest priority
to assign any idle CPU and to avoid pre-emption from other RT tasks.

CRs-Fixed: 2579461
Change-Id: I73feb6613ade240aac7406489b854356e07c6eec
1 file changed