s390/bitops: fix find_next_bit_left

The find_next_bit_left function is broken if used with an offset which
is not a multiple of 64. The shift to mask the bits of a 64-bit word
not to search is in the wrong direction, the result can be either a
bit found smaller than the offset or failure to find a set bit.

Cc: <stable@vger.kernel.org> # v3.8+
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/bitops.h

@@ -693,7 +693,7 @@ static inline int find_next_bit_left(const unsigned long *addr,
 	size -= offset;
 	p = addr + offset / BITS_PER_LONG;
 	if (bit) {
-		set = __flo_word(0, *p & (~0UL << bit));
+		set = __flo_word(0, *p & (~0UL >> bit));
 		if (set >= size)
 			return size + offset;
 		if (set < BITS_PER_LONG)