staging: fix typos "couter" -> "counter"

This patch was generated by

        git grep -l 'couter' drivers/staging | xargs -r perl -p -i -e 's/couter/counter/'

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>