pwm: tegra: Drop duplicated tracking of the parent device

The pwmchip stores a pointer to the parent device, so there is no need
to store another copy in driver private data. Drop struct
tegra_pwm_chip::dev and use the pwm_chip's parent pointer instead.

Link: https://lore.kernel.org/r/225f4bfcb15fb69eb818ddb71d623157c447180a.1707900770.git.u.kleine-koenig@pengutronix.de


Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>