tile: fix bug where fls(0) was not returning 0

This is because __builtin_clz(0) returns 64 for the "undefined" case
of 0, since the builtin just does a right-shift 32 and "clz" instruction.
So, use the alpha approach of casting to u32 and using __builtin_clzll().

Cc: stable@vger.kernel.org
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

arch/tile/include/asm/bitops.h

@@ -77,6 +77,11 @@ static inline int ffs(int x)
 	return __builtin_ffs(x);
 }
 
+static inline int fls64(__u64 w)
+{
+	return (sizeof(__u64) * 8) - __builtin_clzll(w);
+}
+
 /**
  * fls - find last set bit in word
  * @x: the word to search
@@ -90,12 +95,7 @@ static inline int ffs(int x)
  */
 static inline int fls(int x)
 {
-	return (sizeof(int) * 8) - __builtin_clz(x);
-}
-
-static inline int fls64(__u64 w)
-{
-	return (sizeof(__u64) * 8) - __builtin_clzll(w);
+	return fls64((unsigned int) x);
 }
 
 static inline unsigned int __arch_hweight32(unsigned int w)