This patch is a workaround for PR [[ https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=238235 | #238235]].
If users want to disable isochronous transfer on ubt (like me), set loader tunable `hw.ubt.isochronous_transfer=0`.
The default value of `hw.ubt.isochronous_transfer` is 1 that works as same as before.
And the value of ` hw.ubt.isochronous_transfer` can be seen by sysctl.