[RenderEngine] Use highp in shader.

Previously, OETF for PQ transfer function didn't have highp which caused
precesion problem, resulting in noise when hardware composer is in BT2100_PQ
color mode. This patch makes sure we use highp when applying PQ transfer
function.

BUG: 73825729
Test: Build, flash, boot and watch Youtube HDR.
Change-Id: I898e58c641cb9cb678a25d2992695f675b157f9b