x86/emul: Drop X86EMUL_CMPXCHG_FAILED

x86/emul: Drop X86EMUL_CMPXCHG_FAILED

X86EMUL_CMPXCHG_FAILED was introduced in c/s d430aae25 in 2005.  Even at the
time it alised what is now X86EMUL_RETRY (as well as what is now
X86EMUL_EXCEPTION).  I am not sure why the distinction was considered useful
at the time.

It is only used twice; there is no need to call it out differently from other
uses of X86EMUL_RETRY.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Tim Deegan <tim@xen.org>
Acked-by: Jan Beulich <jbeulich@suse.com>