[X86] Remove support for accepting 'fnstsw %eax' and 'fnstsw %al'.

I assume this was done because gas accepted it at one point, but current versions of gas don't.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@331154 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed