x86/headers: Use ABI types consistently in sigcontext*.h

x86/headers: Use ABI types consistently in sigcontext*.h

Use the __u16/32/64 types we standardized on in ABI definitions
- and which most of this header was already using.

This will allow us to more obviously unify the compat header
into the main header.

No change in functionality.

Acked-by: Mikko Rapeli <mikko.rapeli@iki.fi>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/1441438363-9999-6-git-send-email-mingo@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>