NAK: Add support for ffloor, fceil and ftrunc
NAK: Add support for ffloor, fceil and ftrunc
This makes dEQP-VK.glsl.builtin.precision.ceil.highp.scalar pass, as well as:
dEQP-VK.glsl.builtin.precision.floor.highp.scalar
dEQP-VK.glsl.builtin.precision.trunc.highp.scalar