pwm: sprd: Rework how the available channels are counted

pwm: sprd: Rework how the available channels are counted

To be able to convert the sprd driver to pwmchip_alloc() the number of
PWM channels must be known when the driver private data is allocated. So
make sprd_pwm_clk_init() not take a struct sprd_pwm_chip. On the plus
side this allows to drop a member of said driver private data.

Reviewed-by: Chunyan Zhang <zhang.lyra@gmail.com>
Link: https://lore.kernel.org/r/682cbbafbfc4982383d66c3871bb9e52d4e03195.1707900770.git.u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>