bcache: work around a __bitwise to bool conversion sparse warning

Sparse is a bit dumb about bitwise operation on __bitwise types used
in boolean contexts.  Add a !! to explicitly propagate to boolean
without a warning.

Fixes: fcf865e ("block: convert features and flags to __bitwise types")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Kent Overstreet <kent.overstreet@linux.dev>
Link: https://lore.kernel.org/r/20240628131657.667797-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Christoph Hellwig

drivers/md/bcache/super.c

@@ -1416,8 +1416,8 @@ static int cached_dev_init(struct cached_dev *dc, unsigned int block_size)
 	}
 
 	if (bdev_io_opt(dc->bdev))
-		dc->partial_stripes_expensive = q->limits.features &
-			BLK_FEAT_RAID_PARTIAL_STRIPES_EXPENSIVE;
+		dc->partial_stripes_expensive = !!(q->limits.features &
+			BLK_FEAT_RAID_PARTIAL_STRIPES_EXPENSIVE);
 
 	ret = bcache_device_init(&dc->disk, block_size,
 			 bdev_nr_sectors(dc->bdev) - dc->sb.data_offset,