X87: [turbofan] Take the immediate size in account when narrowing ia32/x64 word comparison operators.

  port 2da70f85 (r36136)

  original commit message:
  Trying to re-land http://crrev.com/1948453002 after fixing assembler-x64.cc in http://crrev.com/1962563003.

  Before this patch, we would emit a cmp or test with a memory operand only if both of the operands in the IR were loads.
  Now if either of them is a load and the other one is an immediate, we can use a memory operand if the load representation machine size is wide enough to represent the latter.

BUG=

Review-Url: https://codereview.chromium.org/1967913003
Cr-Commit-Position: refs/heads/master@{#36159}