staging: comedi: Replace "is is" with "is"

This patch replace "is is " with "is". The replacement couldn't be
automated because sometimes the first "is" was meant to be another
word.

Signed-off-by: simran singhal <singhalsimran0@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>