[llvm] [AArch64][InstCombine] Canonicalize whilelo intrinsic (PR #151553)

[Matthew Devereau via llvm-commits]

MDevereau wrote:

With #152140 landed it should be OK to InstCombine whilelo(0,0) to get_active_lane_mask(0,0). I've added the test `whilelo_nxv16i1_0_0`.

https://github.com/llvm/llvm-project/pull/151553