[llvm] [AMDGPU][GlobalISel] Add regbankselect rules for G_FSHR (PR #159818)

[Petar Avramovic via llvm-commits]

https://github.com/petar-avramovic commented:

Need a ll test.
The only pattern I have found for g_fshr is vgpr i32 -> V_ALIGNBIT_B32
only need rule for S32, please correct me if I am wrong here.
Rest of the rules from this patch would be unused since legalizer does the lowering and examples written in mir test would not reach regbankselect/regbanklegalize

https://github.com/llvm/llvm-project/pull/159818