pwm: samsung: Put per-channel data into driver data

Instead of allocating extra data in .request() provide the needed memory
in struct samsung_pwm_chip. This reduces the number of allocations. Even
though now all 5 channel structs are allocated this is probably
outweighed by the reduced overhead to track up to 6 smaller allocations.

Link: https://lore.kernel.org/r/20230705080650.2353391-3-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>