btrfs: cleanup device states define BTRFS_DEV_STATE_WRITEABLE

Currently device state is being managed by each individual int
variable such as struct btrfs_device::writeable. Instead of that
declare device state BTRFS_DEV_STATE_WRITEABLE and use the
bit operations.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
[ whitespace adjustments ]
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index e7f37c4..8c75e55 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1503,7 +1503,7 @@ static noinline int btrfs_ioctl_resize(struct file *file,
 		goto out_free;
 	}
 
-	if (!device->writeable) {
+	if (!test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
 		btrfs_info(fs_info,
 			   "resizer unable to apply on readonly device %llu",
 		       devid);