[PATCH] explicit signed char cast in i386 spin_is_locked

To make spinlock debugging work with -funsigned-char the i386 version
of spin_is_locked() needs to cast to signed char explicitly instead of
just char.  XFS needed -funsigned-char (and currently still has it),
but it doesn't evert hurt.

include/asm-i386/spinlock.h

@@ -39,7 +39,7 @@ typedef struct {
  * We make no fairness assumptions. They have a cost.
  */
 
-#define spin_is_locked(x)	(*(volatile char *)(&(x)->lock) <= 0)
+#define spin_is_locked(x)	(*(volatile signed char *)(&(x)->lock) <= 0)
 #define spin_unlock_wait(x)	do { barrier(); } while(spin_is_locked(x))
 
 #define spin_lock_string \