[llvm] [Hexagon] Provide a custom decoder for Y4_crswap10 (PR #153849)

[Alexey Karyakin via llvm-commits]

quic-akaryaki wrote:

It looks like the operand is not created because there is no bitfield for it in the encoding. I don't know if there is a valid method in LLVM in general to create a fake operand without overriding the whole instruction. In Hexagon, similar cases are handled in a switch inside `HexagonDisassembler::getSingleInstruction`, look for `J4_cmpeqn1_f_jumpnv_nt` and others.
I am fine with the current patch or with extending the switch in `HexagonDisassembler::getSingleInstruction`.

https://github.com/llvm/llvm-project/pull/153849