[AMDGPU][MC] Corrected v_writelane_b32 to fix a decoding bug

Corrected vdst_in to match vdst operand type.
See bug 45193: https://bugs.llvm.org/show_bug.cgi?id=45193

Reviewers: arsenm, rampitec

Differential Revision: https://reviews.llvm.org/D80636