[llvm] AMDGPU: Add testcase for materializing sgpr frame indexes (PR #101306)

[Christudasan Devadasan via llvm-commits]

cdevadas wrote:

These tests written with inline asm constraints are extremely difficult to maintain in terms of retaining the original test scenario. At some point in the future, we are forced to modify them to avoid extreme register pressure (for instance patches like wwm-regalloc) or to make them compilable resulting in losing the purpose of the original test. Because these forced scenarios might disappear and thereafter, these handpicked volatile tests become irrelevant. 

https://github.com/llvm/llvm-project/pull/101306