common: convert to SPDX license tags

These have been scripted conversions then cleaned up by hand as
there was no consistency to the formatting of the license headers in
the common/ directory. Author information was also removed (it's in
the git history) and so now the header format is consistently:

##/bin/bash
# SPDX-License-Identifier: GPL-2.0(+)
# Copyright (c) <date> <owner>. All Rights Reserved.
#
# <file description>

Signed-off-by: Dave Chinner <dchinner@redhat.com>

common/renameat2

@@ -1,26 +1,9 @@
-######
-#
-# renameat2 helpers
-#
-#-----------------------------------------------------------------------
+##/bin/bash
+# SPDX-License-Identifier: GPL-2.0
 # Copyright (c) 2014 Miklos Szeredi.  All Rights Reserved.
 #
-# This program is free software; you can redistribute it and/or
-# modify it under the terms of the GNU General Public License as
-# published by the Free Software Foundation.
-#
-# This program is distributed in the hope that it would be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, write the Free Software Foundation,
-# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
-#-----------------------------------------------------------------------
-#
+# renameat2 helpers
 
-#
 # Setup source or dest
 #
 _setup_one()