pwm: Ensure that pwm_chips are allocated using pwmchip_alloc()

Memory holding a struct device must not be freed before the reference
count drops to zero. So a struct pwm_chip must not live in memory
freed by a driver on unbind. All in-tree drivers were fixed accordingly,
but as out-of-tree drivers, that were not adapted, still compile fine,
catch these in pwmchip_add().

Link: https://lore.kernel.org/r/35f5b229c98f78b2f6ce2397259a4a936be477c0.1707900770.git.u.kleine-koenig@pengutronix.de


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