[llvm] [AMDGPU] Add lit() asm operand modifier for SP3 compatibility. (PR #68839)

[Stanislav Mekhanoshin via llvm-commits]

rampitec wrote:

On a practical note I can see 2 use cases where it may be useful:
1) Force lit encoding to be patched as a relocation. We have a sort of w/a for this, but not at asm level. Again, this boils down to the available representation bits. MI Operand has target bits, but MCOperand does not. So far I do not see a strong evidence we need to make MCOperand heavier than it is now.
2) HW testing of the modifiers applied to literals. Although this does not sound very useful. At the end of the day HW must be tested with SP3 and SP3 must lead here.

https://github.com/llvm/llvm-project/pull/68839