x86: Nuke the supervisor_stack field in i386 thread_info

Nothing references the supervisor_stack in the thread_info field,
and it does not exist in x86_64. To make the two more the same,
it is being removed.
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Brian Gerst <brgerst@gmail.com>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20110806012353.546183789@goodmis.org
Link: http://lkml.kernel.org/r/20140206144321.203619611@goodmis.orgSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

arch/x86/include/asm/thread_info.h

@@ -36,7 +36,6 @@ struct thread_info {
 	unsigned long           previous_esp;   /* ESP of the previous stack in
 						   case of nested (IRQ) stacks
 						*/
-	__u8			supervisor_stack[0];
 #endif
 	unsigned int		sig_on_uaccess_error:1;
 	unsigned int		uaccess_err:1;	/* uaccess failed */