PM / devfreq: sun8i-a33-mbus: Simplify by using more devm functions

Use devm allocators for enabling the bus clock and
clk_rate_exclusive_get(). This simplifies error handling and the remove
callback.

Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Tested-by: Corentin LABBE <clabbe.montjoie@gmail.com>
Link: https://patchwork.kernel.org/project/linux-pm/patch/20250513203908.205060-2-u.kleine-koenig@baylibre.com/


Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>