MFC r368791: disk(9): Fix a few mandoc related errors

• function name without markup: g_io_deliver()
• function name without markup: disk_gone()
• sections out of conventional order: Sh SEE ALSO
• referenced manual not found: Xr MAKE_DEV 9

Actually the man page of MAKE_DEV has never existed.

(cherry picked from commit 9512f75fa8608d150178116ad63672672331b5e8)