[XFS] Fix build warning - xfs_fs_alloc_inode() needs a return statement

SGI-PV: 988141

SGI-Modid: xfs-linux-melb:xfs-kern:32325a
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>

fs/xfs/linux-2.6/xfs_super.c

@@ -872,6 +872,7 @@ xfs_fs_alloc_inode(
 	struct super_block	*sb)
 {
 	BUG();
+	return NULL;
 }
 
 /*