[llvm] [AMX][NFC] Organize tilerow (PR #168193)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

> @RKSimon are you happy with using `t` for tile registers. I recall we discussed somewhere that using different name for GPR and vector registers. Maybe we can start from tile registers since the instructions are small?

Yes, making it easier to distinguish between the main register types would mean its much easier to dynamically determine the instruction enum names (moves between reg types in particular is a mess). 't' for amx tile registers sounds good to me for starters thank you.

https://github.com/llvm/llvm-project/pull/168193