staging: ks7010: fix wait_for_completion_interruptible_timeout return handling

wait_for_completion_interruptible_timeout return 0 on timeout and
-ERESTARTSYS if interrupted. The check for
!wait_for_completion_interruptible_timeout() would report an interrupt
as timeout. Further, while HZ/50 will work most of the time it could
fail for HZ < 50, so this is switched to msecs_to_jiffies(20).

Fixes: 13a9930d ("staging: ks7010: add driver from Nanonote extra-repository")

Signed-off-by: Nicholas Mc Guire <hofrat@osadl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>