pwm: Add missing '\n' in log messages

Message logged by 'dev_xxx()' or 'pr_xxx()' should end with a '\n'.

Fixes: 3ad1f3a3

 ("pwm: Implement some checks for lowlevel drivers")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>