gen8_state: Enable all cube faces
gen8_state: Enable all cube faces

These fields are ignored for non-cube surfaces. For cube surfaces
these fields should be enabled when using TEXCOORDMODE_CLAMP and
TEXCOORDMODE_CUBE.

TODO: Determine if these are the only two modes used in Vulkan.

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler