[ARM] Complete the Thumb1 shift+and->shift+shift transforms.

This saves materializing the immediate.  The additional forms are less
common (they don't usually show up for bitfield insert/extract), but
they're still relevant.

I had to add a new target hook to prevent DAGCombine from reversing the
transform. That isn't the only possible way to solve the conflict, but
it seems straightforward enough.

Differential Revision: https://reviews.llvm.org/D55630

llvm-svn: 349857