Thread through MCSubtargetInfo to relaxInstruction function allowing relaxation to generate jumps with 16-bit sized immediates in 16-bit mode. This fixes PR22097. Reviewers: dwmw2, tstellarAMD, craig.topper, jyknight Subscribers: jfb, arsenm, jyknight, llvm-commits, dsanders Differential Revision: http://reviews.llvm.org/D20830 llvm-svn: 275068