Fix the failing assertion when handle modf
Fix the failing assertion when handle modf

The CTS case is:
dEQP-VK.spirv_assembly.instruction.compute.float32.comparison_2.modfstruct

The prototype is:
modf(x, i) -> GLSL.std.450::modf
frexp(x, exp) -> GLSL.std.450::frexp

For modf, we will store the whole number i. And we translate vectors
to arrays for memory pointers internally. Need to translate them back
before storing. This is the same for frexp.

Change-Id: I61cc4dc39c75c970c562ef527684be3c806f6406

GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc,GPUOpen-Drivers/llpc,googlestadia/llpc,googlestadia/llpc,GPUOpen-Drivers/llpc,googlestadia/llpc,googlestadia/llpc,googlestadia/llpc