pwm: samsung: Consistently use the same name for driver data

The driver uses mostly "chip" to name samsung_pwm_chip pointers:

$ git grep -Pho 'samsung_pwm_chip \*[a-zA-Z0-9_]+(*nla:[a-zA-Z0-9_(])' v6.5-rc1 -- drivers/pwm/pwm-samsung.c | sort | uniq -c
     10 samsung_pwm_chip *chip
      6 samsung_pwm_chip *our_chip
      1 samsung_pwm_chip *pwm

However "chip" is supposed to be used for struct pwm_chip pointers and
"pwm" for struct pwm_device pointers. So consistently use "our_chip".

Link: https://lore.kernel.org/r/20230929161918.2410424-11-u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>