ntoskrnl.exe: Fix SIB_INDEX() to use REX_X, not REX_R.

[Sebastian Lackner]

On 12.04.2016 08:19, Ken Thomases wrote:
> Signed-off-by: Ken Thomases <ken at codeweavers.com>
> ---
> See <http://source.winehq.org/source/programs/winedbg/db_disasm64.c#0992> or
> <http://wiki.osdev.org/X86-64_Instruction_Encoding#Encoding>, for confirmation.
> 
>  dlls/ntoskrnl.exe/instr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 

Good catch, thanks.