pwm: xilinx: Simplify using devm_ functions

pwm: xilinx: Simplify using devm_ functions

There are devm variants for clk_prepare_enable() and pwmchip_add(); and
clk_prepare_enable() can be done together with devm_clk_get(). This
allows to simplify the error paths in .probe() and drop .remove()
completely.

With the remove callback gone, the last user of platform_get_drvdata()
is gone and so the call to platform_set_drvdata() can be dropped, too.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Reviewed-by: Sean Anderson <sean.anderson@seco.com>
Link: https://lore.kernel.org/r/20240628063524.92907-2-u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>