pwm: berlin: use consistent naming for variables

pwm: berlin: use consistent naming for variables

A struct berlin_pwm_chip * is now always called "bpc" (instead of "pwm"
which is usually used for struct pwm_device * or "chip" which is usually
used for struct pwm_chip *). The struct pwm_device * variables were
named "pwm_dev" or "pwm"; they are now always called "pwm".

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>