[OVER TEMP CAL] -- Update Valid Model Check

Updates the isValidOtcLinearModel function to ensure that
over-temp linear model updates are accepted for devices
where gyro temperature sensitivity is nearly zero.

Tip of G3: 201100998
Bug: 110109779
Test: Built and device tested.

Change-Id: If461ac7f915774baf03c406ee3f7db32b4fe3190