xfs: standardize AG block number formatting in ftrace output

Always print allocation group block numbers in hexadecimal and preceded
with the unit "agbno".

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>