[AMD] Reland sinking the 2nd tt.load after local_load's (triton-lang#…

…4935)

This PR adds more restrictions about when should we apply
the sched-load optimizations and un-revert
triton-lang#4823.

We will only apply the optimization when all of the following is
satisfied:
1. pureMatmulProblem, i.e. 1 `tt.dot` in the main loop
2. two `tt.load`s in the main loop
3. 2nd `tt.load` is ahead of the `tt.dot`
4. 1st user of 2nd `tt.load` is after the `tt.dot`
5. tile size is large enough, i.e. nonKDim >= 128 and kDim >= 64

(cherry picked from commit 4f6f768)