[globalisel][tablegen] Stop hard-coding the emitted instruction ID to 0. NFC
[globalisel][tablegen] Stop hard-coding the emitted instruction ID to 0. NFC

The next commit will add support for multi-instruction emission so we need to
start allocating instruction ID's instead of hard-coding them to 0.



git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@317057 91177308-0d34-0410-b5e6-96231b3b80d8

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