pwm: hibvt: Consistently name driver data hi_pwm_chip

pwm: hibvt: Consistently name driver data hi_pwm_chip

The driver uses two different names for variables of type
hibvt_pwm_chip:

	$ git grep 'struct hibvt_pwm_chip \*' v6.8-rc1 drivers/pwm/pwm-hibvt.c
	v6.8-rc1:drivers/pwm/pwm-hibvt.c:static inline struct hibvt_pwm_chip *to_hibvt_pwm_chip(struct pwm_chip *chip)
	v6.8-rc1:drivers/pwm/pwm-hibvt.c:       struct hibvt_pwm_chip *hi_pwm_chip = to_hibvt_pwm_chip(chip);
	v6.8-rc1:drivers/pwm/pwm-hibvt.c:       struct hibvt_pwm_chip *hi_pwm_chip = to_hibvt_pwm_chip(chip);
	v6.8-rc1:drivers/pwm/pwm-hibvt.c:       struct hibvt_pwm_chip *hi_pwm_chip = to_hibvt_pwm_chip(chip);
	v6.8-rc1:drivers/pwm/pwm-hibvt.c:       struct hibvt_pwm_chip *hi_pwm_chip = to_hibvt_pwm_chip(chip);
	v6.8-rc1:drivers/pwm/pwm-hibvt.c:       struct hibvt_pwm_chip *hi_pwm_chip = to_hibvt_pwm_chip(chip);
	v6.8-rc1:drivers/pwm/pwm-hibvt.c:       struct hibvt_pwm_chip *hi_pwm_chip = to_hibvt_pwm_chip(chip);
	v6.8-rc1:drivers/pwm/pwm-hibvt.c:       struct hibvt_pwm_chip *pwm_chip;
	v6.8-rc1:drivers/pwm/pwm-hibvt.c:       struct hibvt_pwm_chip *pwm_chip;

Most functions use "hi_pwm_chip" as name. Make use of this in the
remaining two functions (that used "pwm_chip" before, which isn't
optimal as this is a type name, too).

Link: https://lore.kernel.org/r/66ff5a9b00889ff0c576afc783424478fbbb9853.1707900770.git.u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>