powerhint: raise cam.uclamp_min to 250 during CAMERA_STREAMING_EXTREME

Increase the minimum operating frequency of the cam group to mitigate mutex contention and thereby reduce frame drops during 240fps slow-motion recording.

This solution synchronize from ag/25825179.

Test: GCA, CTS
Bug: 315422971
Change-Id: I8ab72ef5980edf881c034789d947dc578659cbe2
3 files changed