xfs_db: identify the minlogsize transaction reservation

xfs_db: identify the minlogsize transaction reservation

Right now, we don't make it easy to spot the transaction reservation
used to compute the minimum log size in userspace:

# xfs_db -c logres /dev/sda
type 0 logres 168184 logcount 5 flags 0x4
...
type 25 logres 760 logcount 0 flags 0x0
type -1 logres 547200 logcount 8 flags 0x4

Type "-1" doesn't communicate the purpose at all, it just looks like a
math error.  Help out the user a bit by printing more information:

minlogsize logres 547200 logcount 8

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>