Fix build with expensive checks enabled
Fix build with expensive checks enabled

Include of llvm/IR/Verifier.h was removed from HexagonCommonGEP.cpp in r289604
as unused. In fact it is required when expensive checks are enabled, because
it declared function `verifyFunction`, which is called in conditionally compiled
part of the file.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@290170 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm