spirv: Image size queries can be 64bit in SPIR-V
OpenCL array size queries issue a SPIR-V OpImageQuerySize[Lod] op which returns a size_t-sized value. That means it can be 64-bit.
Don't make nir deal with this and just upconvert to the bit size SPIR-V is expecting if it doesn't match.
I guess I haven't re-run the test_kernel_image_methods test all the way through since we switched to 64bit SPIR-V.