gpio: aggregator: simplify aggr_parse() with scoped bitmap

The bitmap allocated in aggr_parse() is always freed before the function
returns so use __free(bitmap) to simplify it and drop the goto label.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20240930163207.80276-1-brgl@bgdev.pl


Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>