[MemorySSA] MemorySSA should not model debuginfo, and need not update it.
[MemorySSA] MemorySSA should not model debuginfo, and need not update it.

Reverts the change in r371084, but keeps the test.
After r371565, debuginfo cannot be modelled in MemorySSA, even with a
non-standard AA pipeline.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@371573 91177308-0d34-0410-b5e6-96231b3b80d8

GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm