[XFS] avoid using pid_t in ioctl ABI

SGI Modid: xfs-linux:xfs-kern:177165a
Signed-off-by: Nathan Scott <nathans@sgi.com>

fs/xfs/xfs_fs.h

@@ -165,7 +165,7 @@ typedef struct xfs_flock64 {
 	__s64		l_start;
 	__s64		l_len;		/* len == 0 means until end of file */
 	__s32		l_sysid;
-	pid_t		l_pid;
+	__u32		l_pid;
 	__s32		l_pad[4];	/* reserve area			    */
 } xfs_flock64_t;