pwm: bcm2835: Simplify using devm functions

pwm: bcm2835: Simplify using devm functions

With devm_clk_get_enabled() the call to clk_disable_unprepare() can be
dropped from the error path and the remove callback. With
devm_pwmchip_add() pwmchip_remove() can be dropped. Then the remove
callback is empty and can go away, too. With bcm2835_pwm_remove() the only
user of platform_get_drvdata() is gone and so platform_set_drvdata() can
be dropped from .probe(), too.

Also use dev_err_probe() for simplified (and improved) error reporting.

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Uwe Kleine-König <[email protected]>
Signed-off-by: Thierry Reding <[email protected]>