[Alignment] fix dubious min function alignment
[Alignment] fix dubious min function alignment

Summary:
This was discovered while introducing the llvm::Align type.
The original setMinFunctionAlignment used to take alignment as log2, looking at the comment it seems like instructions are to be 2-bytes aligned and not 4-bytes aligned.

Reviewers: uweigand

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D67271

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@371204 91177308-0d34-0410-b5e6-96231b3b80d8

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