x86: Get rid of 'dubious one-bit signed bitfield' sprase warning

This very noisy sparse warning appears on almost every file in the
kernel:

  CHECK   init/main.c
  arch/x86/include/asm/thread_info.h:43:55: error: dubious one-bit signed bitfield
  arch/x86/include/asm/thread_info.h:44:46: error: dubious one-bit signed bitfield

This patch changes sig_on_uaccess_error and uaccess_err flags to unsigned
type and thus fixes the warning.
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>
Acked-by: Andy Lutomirski <luto@mit.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/include/asm/thread_info.h

@@ -40,8 +40,8 @@ struct thread_info {
 						*/
 	__u8			supervisor_stack[0];
 #endif
-	int			sig_on_uaccess_error:1;
-	int			uaccess_err:1;	/* uaccess failed */
+	unsigned int		sig_on_uaccess_error:1;
+	unsigned int		uaccess_err:1;	/* uaccess failed */
 };
 
 #define INIT_THREAD_INFO(tsk)			\