Imgtec Waiver for texture_gather*cube*depth32f*

Imgtec Waiver for texture_gather*cube*depth32f*

Some versions of Imagination Technologies G6200, G6230, G6400, and
G6430 Rogue Series 6 GPU's are unable to correctly filter CEM corners
with F32 textures, this includes the ability to gather texels for texel
gather instructions.

This CL excludes the affected tests from mustpass.

Affects:

All dEQP-VK.glsl.texture_gather.basic.cube.depth32f* tests except:

dEQP-VK.glsl.texture_gather.basic.cube.depth32f.no_corners*

Components: Vulkan

VK-GL-CTS issue: 336

Change-Id: I4e20d887ad2901f78a7af326035d7a2a9ae5e76a