Fix Rgba16fTests@testTransferFunctionsShader test

RGBA16F bitmaps used as an SkBitmapShader would not set the hasLinearTexture
flag in the program description, causing a shader to be generated without
the proper opto-electronic transfer function.

Bug: 35482305
Test: bit -t CtsUiRenderingTestCases:android.uirendering.cts.testclasses.Rgba16fTests
Change-Id: I23354f8189a6b27b677eac9df82677e91282a31d