Print rd(4) capacity and geometry info as sd(4) and wd(4) do.

Before:
rd0 at hpibbus1 slave 0 punit 0: 7937H
rd0: 698 cylinders, 13 heads, 1116102 blocks, 512 bytes/block

After:
rd0 at hpibbus1 slave 0 punit 0: 7937H
rd0: 544 MB, 698 cyl, 13 head, 123 sec, 512 bytes/block x 1116102 blocks

(tsutsui)