Input is handled in softirq context, but when pasting we may
need to sleep. speakup_paste_selection() currently tries to
bodge this by busy-waiting if in_atomic(), but that doesn't
help because the ldisc may also sleep.
For bonus breakage, speakup_paste_selection() changes the
state of current, even though it's not running in process
context.
Move it into a work item and make sure to cancel it on exit.