nir/fold_16bit_sampler_conversions: Fix type mismatches.
Closes #5996 (closed)
Fixes: fb29cef8 ("nir: add many passes that lower and optimize 16-bit input/outputs and samplers")
Closes #5996 (closed)
Fixes: fb29cef8 ("nir: add many passes that lower and optimize 16-bit input/outputs and samplers")