pwm: jz4740: Consistently name driver data "jz"

Most but not all pointers to driver data are already called "jz":

	$ git grep 'struct jz4740_pwm_chip \*' v6.5-rc1 -- drivers/pwm/pwm-jz4740.c
	v6.5-rc1:drivers/pwm/pwm-jz4740.c:static inline struct jz4740_pwm_chip *to_jz4740(struct pwm_chip *chip)
	v6.5-rc1:drivers/pwm/pwm-jz4740.c:static bool jz4740_pwm_can_use_chn(struct jz4740_pwm_chip *jz,
	v6.5-rc1:drivers/pwm/pwm-jz4740.c:      struct jz4740_pwm_chip *jz = to_jz4740(chip);
	v6.5-rc1:drivers/pwm/pwm-jz4740.c:      struct jz4740_pwm_chip *jz = to_jz4740(chip);
	v6.5-rc1:drivers/pwm/pwm-jz4740.c:      struct jz4740_pwm_chip *jz = to_jz4740(chip);
	v6.5-rc1:drivers/pwm/pwm-jz4740.c:      struct jz4740_pwm_chip *jz4740 = to_jz4740(pwm->chip);
	v6.5-rc1:drivers/pwm/pwm-jz4740.c:      struct jz4740_pwm_chip *jz4740;

Adapt the two variables called "jz4740" to use the same name for
consistency.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Link: https://lore.kernel.org/r/20230808062608.897710-1-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>