Avoid unecessary opsize byte in segment move to memory

Segment moves to memory are always 16-bit. Remove invalid 32 and 64
bit variants.

Recommiting with missing clang inline assembly test change.

Fixes PR34478.

Reviewers: rnk, craig.topper

Subscribers: llvm-commits, hiraditya

Differential Revision: https://reviews.llvm.org/D39847

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@318797 91177308-0d34-0410-b5e6-96231b3b80d8
9 files changed