storage_util: Prefer generic FICLONE over btrfs/xfs defines

After my change to the original patch that resulted in commit
8ed874b3 it was brought to my attention that all three defines
are the same: FICLONE = BTRFS_IOC_CLONE = XFS_IOC_CLONE (as
documented in ioctl_ficlone(2)). Therefore we should prefer
generic FICLONE over 'specific' defines for btrfs/xfs.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NAndrea Bolognani <abologna@redhat.com>

src/storage/storage_util.c

@@ -46,14 +46,14 @@
 # include <selinux/selinux.h>
 #endif
 
-#if HAVE_LINUX_BTRFS_H
+#ifdef FICLONE
+# define REFLINK_IOC_CLONE FICLONE
+#elif HAVE_LINUX_BTRFS_H
 # include <linux/btrfs.h>
 # define REFLINK_IOC_CLONE BTRFS_IOC_CLONE
 #elif HAVE_XFS_XFS_H
 # include <xfs/xfs.h>
 # define REFLINK_IOC_CLONE XFS_IOC_CLONE
-#elif defined(FICLONE)
-# define REFLINK_IOC_CLONE FICLONE
 #endif
 
 #include "datatypes.h"