clk: mediatek: reset: Return regmap's error code

device_node_to_regmap() can return different errors, and it's better
practice to pass them to callers.

Clean up the hardcoded -EINVAL and use PTR_ERR(regmap) instead.

Signed-off-by: Fei Shao <fshao@chromium.org>
Link: https://lore.kernel.org/r/20240717115919.975474-1-fshao@chromium.org


Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>