[SimplifyCFG] mergeConditionalStoreToAddress(): try to pacify MSAN
[SimplifyCFG] mergeConditionalStoreToAddress(): try to pacify MSAN

MSAN bot complains that there is use-of-uninitialized-value
of this FreeStores later in IsWorthwhile().
Perhaps FreeStores needs to be stored in a vector?

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@372262 91177308-0d34-0410-b5e6-96231b3b80d8

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