[Intrinsic] Add fixed point division intrinsics.

Summary:
This patch adds intrinsics and ISelDAG nodes for
signed and unsigned fixed-point division:

  llvm.sdiv.fix.*
  llvm.udiv.fix.*

These intrinsics perform scaled division on two
integers or vectors of integers. They are required
for the implementation of the Embedded-C fixed-point
arithmetic in Clang.

Patch by: ebevhan

Reviewers: bjope, leonardchan, efriedma, craig.topper

Reviewed By: craig.topper

Subscribers: Ka-Ka, ilya, hiraditya, jdoerfert, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70007