[ARM] Inline callee if its target-features are a subset of the caller

Summary:
Similar to X86, it should be safe to inline callees if their
target-features are a subset of the caller. As some subtarget features
provide different instructions depending on whether they are set or
unset (e.g. ThumbMode and ModeSoftFloat), we use a whitelist of
target-features describing hardware capabilities only.

Reviewers: kristof.beyls, rengolin, t.p.northover, SjoerdMeijer, peter.smith, silviu.baranga, efriedma

Reviewed By: SjoerdMeijer, efriedma

Subscribers: dschuff, efriedma, aemerson, sdardis, javed.absar, arichardson, eraman, llvm-commits

Differential Revision: https://reviews.llvm.org/D34697

llvm-svn: 307889