x86/entry: Change stale function name in comment to error_return()

Correct old function name error_exit() in the comment to what it is now
called: error_return().

  [ bp: Provide a commit message and massage. ]

Signed-off-by: Jingyu Wang <jingyuwang_vip@163.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20220618154238.27749-1-jingyuwang_vip@163.com