x86/asm/entry: Make user_mode() work correctly if regs came from VM86 mode

x86/asm/entry: Make user_mode() work correctly if regs came from VM86 mode

user_mode() is now identical to user_mode_vm().  Subsequent patches
will change all callers of user_mode_vm() to user_mode() and then
delete user_mode_vm().

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brad Spengler <spender@grsecurity.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/0dd03eacb5f0a2b5ba0240de25347a31b493c289.1426728647.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>